Pitfalls in detail

probably currently the fastest and most available GSM / UMTS / ... network in Germany

the voice quality I find subjectively better than eg in e-net

but

1.)
it begins with the migration (change of operator)

it is casually mentioned very small print that
a) a Migration Policy b) 25 Euro are needed when Altprovider, making the switch from legacy bidding works

it is obviously created that the migration does not work and you automatically get a new phone no. So it actually worked for me only with the third attempt

You could make more insightful (eg via checkbox) that you have stored eg dismissal when Altan bidder and the necessary porting fee.

2.)
Although you pay for the SIM card, for example, by direct debit,
takes the first charge via direct debit again five days (allegedly because credit check). jo, bitter, if you want to recharge, which is well written but only in 5 days.

3.)
and I find that really the hammer:

a "fast" zubuchen or debiting tariff packages do not exist. It takes about 3 weeks before we can announce the old Surf package and a new example has larger active. Well, now I have 3 weeks after mobile internet

4.)
the customer via e-mail is nice, but needs at least 1-2 days of reaction time

5.) Use of surface congstar I feel much more confusing and less transparent than other operators. The remaining balance can not see online, any more than the data consumption.