How to reactivate an expired prepaid number?

Hello friends,

I am new in Germany and got a prepaid sim card from O2. I assigned my social network to this number. After some months, the app for my social network was accidentally deleted from my mobile cell! I installed it again but it needs my old (expired) phone number by O2. I did not charge it for some months and now I see the number is not activated anymore. I called the O2, they said the number is dead!
Could someone help me how can I ever survive from this damn situation?
I have all my activities in that network and the network has a security that no one can retrieve an account without accessing to the assigned phone number!
PLEASEEEE show me ANY solution that I can order, buy, or ... to have my old number again or at least once more!

Thank you with all respects.