The problem is now solved. Thanks to all (including Thomas and Lars) who have contributed. I guess it was all thanks to the forum at the end of the day since we were not able to clearly communicate with a representative over the hotline.
As a general feedback, Vodafone needs to be able to hire "at least some" customer representatives who can speak English (not necessarily fluently, B2-C1 level should be OK). We have talked to around 10-12 customer representatives only one of whom can communicate in English. And, she was able to sell us the TV package by the way.
Is Vodafone Germany not aware of the fact that they are operating in a country that receives a lotof migrants day by day, including expats? They do not even have the option of an English-speaking representative when you choose "Kabel" at the beginning. If you choose "Mobilfunk" at the beginning, you have the option of calling out "operator" to connect to an English-speaking representative IF you are lucky enough.
