I converted my number to a bill-pay last week, and I had to submit proof of residence for that. I think they also asked for proof of ID (passport) and proof of residence status.
> I never tried it, but apparently you can buy topup vouchers at retailers also for cash.
You can, yep. We do it once a month for my partner's mum who would be considered "unbanked".
Only a handful of EU countries didn't follow through with the ruling [1]
Landline is a bit different, as you need proof of residence to contract it anyway.
[0] https://hudoc.echr.coe.int/eng#{%22itemid%22:[%22001-200442%...}
[1] https://prepaid-data-sim-card.fandom.com/wiki/Registration_P...
Claim was "you can't get a SIM card without a passport or ID" which was disputed.
And lastly, especially if you live in west german you can just take a train to the netherlands and by a sim there, no registration required.
£25 for 12Gb of data would be ripoff here, unless it's roaming data.
EE [0] are one of the bigger carriers here, and the only ones with decent coverage where I live, this is their list of plans. You can get cheaper, but it often comes with limited speeds.