congstar Explained: Prepaid Allnet Flats, 28-Day Billing and Telekom's Network
congstar is Telekom's budget brand. Here is how its prepaid Allnet Flat tiers work, why 28-day billing means 13 payments a year, and who should choose it over a monthly contract.
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If you live in Germany, or move there, you will meet congstar quickly. It is one of the most visible budget mobile brands, and the reason is simple: it runs on the same network as its parent, Deutsche Telekom.
The facts here come from public sources including the German Wikipedia entry and mobile-news coverage from 2024 and 2025. Prices change often, so treat any number below as an example and confirm it on congstar's site.
Who is congstar?
congstar was founded on 11 November 2004 as congster GmbH in Darmstadt, and the congstar brand came in 2007. It is based in Cologne and is wholly owned by Telekom Deutschland GmbH. Its mobile services use the Telekom Deutschland network. The company said it had more than seven million customers in April 2025.
How the prepaid range works
congstar's prepaid range, "Prepaid wie ich will", launched in April 2019 and has three parts: ready-made packages, the Prepaid Allnet Flat and a modular tariff builder. LTE has been included in every prepaid tariff since July 2020, and 5G has been available since 23 January 2024.
Based on 2025 coverage, the Allnet Flat tiers looked like this:
| Tier | Data | Network speed | Price (per 28 days) |
|---|---|---|---|
| XS | 1 GB | LTE up to 25 Mbit/s | about 5 euros |
| S to XL | 5 to 40 GB | 5G | up to about 16 euros for XL |
All include calls and SMS flats, and they can be booked without a contract. At one point the starter pack was cut to 1 euro from 4.99 euros. Check whether that offer is running when you order.
The 28-day trick
Many prepaid tariffs bill every 28 days rather than every calendar month. That sounds identical until you do the arithmetic: a year has 365 days, which is about 13 periods of 28 days. So a 5 euro tariff costs roughly 65 euros per year, not 60.
It is a small difference, but it matters when you compare a 28-day tariff with a monthly one. Multiply the per-period price by 13 and the monthly price by 12, then compare the totals.
Prepaid or contract?
congstar also offers postpaid plans, with a fixed term or a "Flex" option that can be cancelled at month end. The main trade-offs:
Deals for Congstar
3 offers running now
- Prepaid gives you freedom and easy budgeting. It suits students, newcomers, second phones and travellers.
- Postpaid can suit heavy data users and anyone who wants a subsidised phone, but it commits you for longer unless you pay for Flex.
Who should pick congstar?
- Anyone who wants Telekom network quality at a budget price.
- People who value cancelling any time.
- Households with a spare SIM for a tablet or a child's phone.
If you live in a spot with weak Telekom coverage, check a coverage map first, since the network is the same for all of its brands.
Current congstar discounts
congstar often runs starter-pack offers and promotional pricing. Every active offer we list, with end dates, is on one page: see all congstar coupons. The best two or three also appear in the deals box in this article. Penrift may earn a commission if you use them, as described in our affiliate disclosure.
Bottom line
congstar is not the cheapest name in German mobile, and it does not claim to be. It is the one that combines a major network with prepaid simplicity. Do the 28-day maths, check your coverage and pick the smallest tier that covers your data use.
Product lineups, prices and availability change often. Check current specs and retailer terms before you buy. See our editorial policy and affiliate disclosure.
