How can I get my number back?

My problem is:

I had a prepaid number. I did not pay for it for 3 months, since I was not in the country. Yesterday I received an email that my number has been blocked. I asked my friend to pay for my number, but he was told that the number was already blocked and I needed to contact Customer Service. I don't want to lose my number, it's important! But at the moment I'm also not in the country. I can't log in to my T-mobile account because I need to receive a confirmation code to my number in order to log in. But it is blocked and the code does not come. 

Is it possible to contact Customer Service via chat? or via email. I need to urgently save my number before it can be sold to someone else. 

Thank you.