5G connection not available and out of contract after already been used

Hello,

In the end of April I have signed an O2 Mobile L contract with a new device via Check24.

As stated in the contract I have received from Check24 and was from O2 this is including 5G. The first month everything worked smooth and I was pretty satisfied with the coverage of 5G  however, after my first monthly payment 5G has stopped working entirely.

Firstly I called the customer service were they informed me that there is a technical issue in my area and they are looking for a solution. At the same time a colleague of mine, and customer of O2 had 5G just next to me.

I decided to go to a O2 store and the employees show me that in the O2 system it looks like I am not having the 5G option in my contract. Since no-one was speaking English and my German is limited I was not able to fully explain and understand the situation. 

How can that be possible since I signed it in my contract and also used it all May? Is there any explanation or someone facing a same issue?

I have already reached out to Check24 as well but I wanted to ask here as well. 

Thanks in advance