Today I called a friend of mine and something weird was going on. When he picked up the call, it was not showing my phone number on the caller ID but a different mobile number apparently from Romania. We could hear each other only badly and with a huge delay.
I then called again, and this glitch (?) was gone. Could it be some kind of hack/security issue?
To give more detail, we both have a German mobile provider. I am currently in the Netherlands and have been calling from the train, while my friend is currently in Germany.