I keep trying to upgrade but keep getting message of unable to complete, why?

I'm so frustrated I'm ready to pull my hair out!  I try to upgrade and go through the process until the very end when it says "We are unable to change your plans at this time. Please try again later. If this continues to fail, please contact Customer Support." but the maze to get any support is CRAZY!  I changed payment methods and that could be what is stopping me, or maybe there's something about my computer that is causing the issue but since there isn't someone I can simply call to ask I go from one area to the next SEARCHING for an answer I don't know the question to!  If anyone has some idea what might be the problem will you please respond? 

THANK YOU!!

Vickie