Microsoft refuses to help me redeeming my gift cards

Hello,

For a long time now I try to get gift cards redeemed to my Xbox account. Both the console and the Microsoft Website don't accept the codes.

I contacted the support and after a long time of waiting I got the response that I bought the code at another place than I am living.

But this is not true. I live in Germany and I bought the cards in a local shop. I provided the support both the receipt and my ID which indicate my statement is correct. Yet I got no further support. Contacting Germany's Microsoft address was ignored.

I don't know what the problem and neither why I don't receive help. If there is an invalid place of living in my account I cannot see it nor does the support fix that for me.

What can I do?

If I can't do anything, where can I find the relevant Terms of Usage for legal steps?

:)