I have connected to the T Mobile Hotspot at Munich Airport. Paid 8 Euros to get access. During the sign up I was asked about email, etc. After that I read the following:
"When paying with your credit card you can print out a personalised receipt. This receipt can be stored on your device as a PDF before you login and be printed at a later date. Please note that it is no longer possible to get a receipt after you have logged in."
So, I cannot get a receipt if I miss the first chance, which I am not alerted about. Unacceptable! However, the reason I am writing is not this. The reason is their entire website does not have a single email, or phone number for complaints, issues. How convenient and how disgusting. They only list a phone number for "help", which charges money for each connection. Really really bad business practice.