@Amrando
Lidl is a nationwide chain, but note that their supermarkets tend to be rather outside city centers (search for stores
here). In order to benefit from the referral program just use the number given in the previously linked activation instructions - it's actually mine.
When travelling by ICE or IC-trains make sure you take your seat in a car equipped with repeaters so you get a better signal (but don't expect too much 3G coverage, especially on ICE trains which pass many tunnels). These cars are marked with the following sign:
