So what should I do?? I can't pay from Russia. Using a US card at US rates is too expensive for me.
Just to be clear, if you have an international card that works, you simply need to enter your actual billing address, then there will be no problems with your plan.
If we see a US card buying a plan in Ethiopia, with heavy usage in Russia, it's going to flag your plan up in our system and we'd want to see evidence you do actually live in Ethiopia.