In short: Up to €20 there are more unlimited options, but Simsalasim at €10 stays the cheapest unlimited plan and the only one with unlimited travel data in 100 countries.

  1. Simsalasim – #1.
    €10/month, unlimited + 100 countries + number, on the Telefónica (O2) network, the cheapest unlimited plan.
  2. congstar Allnet Flat XS – €15.00* / 15 GB.
    Telekom network, fixed allowance.
  3. sim.de – €19.99* / Unlimited on demand.
    Unlimited (on demand), data only, on the Telefónica (O2) network.
  4. 1&1 Unlimited – €19.99* / unlimited.
    True unlimited, but double the price of Simsalasim.
  5. O2 Mobile – €19.99* / 15 GB.
    Telefónica (O2) network, fixed allowance (true unlimited from €24.99).
  6. otelo – €19.99* / 50 GB.
    Vodafone network, fixed allowance.
  7. SIMon mobile – €21.99* / 150 GB.
    Vodafone network, the largest data pack, just over €20.

Verdict: Under €20, 1&1 and sim.de also offer unlimited, but pricier and without travel. Simsalasim stays the value winner.

*Prices and offers can change over time (as of October 2026).