congstar in review: What the Telekom network is really worth for 10 euros

Ten euros for five gigabytes. On paper, that's not an offer in 2026 – it's an insult. At Lycamobile you get the same five gigabytes for two euros, including 5G. And yet congstar has had a surprisingly loyal customer base for years. The reason isn't in the spec sheet, it's in the network behind it.

For the record: congstar has been a partner of internet-deals.de since July. That's exactly why we're going into detail here about the points that speak against these plans. An advertising text wouldn't do you any good.

The four unlimited calls plans at a glance

congstar is Deutsche Telekom's secondary brand and runs on the original D1 network. The mobile plan portfolio is compact – here are the numbers as of August 2026:

All four include unlimited calls to all German networks and unlimited texts. And all four are available in the Flex variant no minimum term – that's the point that's easy to overlook, even though it's the most important one. We'll come back to that.

Two things stand out immediately. First: the Allnet Flat S has no 5G and no eSIM. It runs on the LTE network, like a plan from 2019. Second: the jump from S to M costs five euros and gets you ten gigabytes plus 5G plus eSIM. That's the best five-euro upgrade in the entire portfolio, and it makes the S the wrong choice for almost everyone.

The real selling point is called D1

congstar doesn't sell gigabytes, congstar sells network quality. The SIM card runs on the Telekom network – not a stripped-down offshoot, but the very same network the significantly more expensive MagentaMobil plans use. Anyone who regularly commutes between cities, works on the train, or lives in a rural area knows the difference: it's the spot where O2 customers hold their phone out the window and Telekom customers are still on a call.

Fair is fair, though. In a well-covered city, the gap between the three networks has become small, and O2 is enough for Instagram on the bus. The D1 surcharge pays off where the network map has gaps – and only there. We've covered which network performs where in our network coverage comparison coverage guide. Check your own address and commute route before signing up, not the nationwide average.

The price comparison, without sugarcoating

Now for the uncomfortable part. Against the discounters, congstar loses on every pure price comparison, and by a clear margin:

• The Unlimited Calls Plan S costs €10 for 5GB without 5G. Lycamobile charges for 5GB with with 5G €2.00, Primavolt offers 15GB with 5G for €5.99. Both, however, run on the O2 network. Our recommendation is still clear: stay away from the S. Either you want D1 – then get the M – or you want to save money, then you're better off with the unlimited calls plans under €10 better served.
• The Allnet Flat M is the plan this is really about. €15 for 15GB, 5G, eSIM, D1 and no minimum term. Blau offers 15GB for €10.99, but on the O2 network and with the usual fine print. Four euros extra per month for the Telekom network and full flexibility – that's a price you don't need to think twice about.
• The Allnet Flat L with 25GB for €20 is solid, and the XL with unlimited data for €30 is the plan for people who actually stream on the go. Honest question first: do you need that? Most people use less than 15GB a month. How to work out your actual usage in two minutes is covered in our guide How much data allowance do I need? – if you end up at 12GB there, you're paying ten euros a month for nothing but headroom with the XL.

If you want to compare the plans directly against the competition: in the Side-by-Side Comparison you can see any two plans with their effective monthly costs side by side. All current congstar terms are available on our congstar overview.

The DSL plan: decent, but with a cap

In addition to mobile plans, congstar also sells landline plans. There is exactly one plan, the Internet & Phone Flat: €24.99 instead of €34.99, up to 50 Mbit/s over the Telekom landline network, unlimited calls to German landlines, WiFi router included, 24-month term.

For context: Telekom charges €39.95 for the same 50 Mbit/s line in MagentaZuhause S. Fifteen euros' difference per month for technically identical access – that's the secondary-brand principle in its purest form. On the other hand, there's 1&1 DSL 50 for €19.99, though without unlimited calls, and Deutsche Glasfaser delivers 100 Mbit/s for exactly the same €24.99 – if fibre is available at your address.

And there's the cap: 50Mbit/s isn't the entry level at congstar, it's the maximum. If you want 100, 250 or 1,000Mbit/s, you're in the wrong place here and should first check what's actually possible at your connection point – the difference between connection types is bigger than the difference between providers, see DSL, cable, or fibre. If you can't get a landline connection at all, congstar Homespot offers a stopgap solution: internet for your home via the mobile network, without a technician appointment.

One more important thing: unlike the mobile plans, the DSL plan has a 24-month commitment. The flexibility that congstar uses as a selling point for mobile doesn't apply to landline.

The two points you should know before you click

First, the discounted price is real. The €10, €15, €20 and €30 are promotional prices; the list prices are €15, €20, €30 and €40. How long the promotion applies to you is stated in the order process, not in the ad banner – read that line before you confirm. The consolation: with a no-minimum-term Flex plan, getting out is trivial. If the price goes up, you cancel at the end of the month and take your number with you. How number porting works is explained in our guide Cancelling a mobile plan. This is exactly where congstar has the edge over discounters with 24-month contracts: you can take advantage of the offer without tying yourself down for two years.

Second, watch the version. congstar offers its plans with and without a contract term. The no-minimum-term Flex variant is the interesting one, and it's not selected by default. One wrong click during the order process and you've signed up for 24 months, for a plan whose whole appeal was the flexibility to cancel.

Bottom line

congstar is not a bargain and doesn't try to be. It's the compromise for people who want the Telekom network but not the Telekom prices – and who don't want to commit. The plan that fits that bill is the Allnet Flat M for fifteen euros: 15 GB, 5G, eSIM, D1, cancel monthly. That's a clean offer with no catch.

We'd skip the S, and only go for the XL if you genuinely max out your data allowance. The DSL plan is only worth a look if 50 Mbit/s is enough for you and you need the unlimited calls – otherwise fibre or cable at the same address are often the better deal. And if, in the end, all you care about is price and your network works fine everywhere anyway: then congstar isn't your provider, and that's perfectly fine.

Not sure whether the D1 surcharge is worth it at your address? Through our callback form we'll take a look with you for free – no waiting on hold, no sales pressure.