I know that really sucks. When you were playing as Guest did you still have 100% of your progress? If so were you regularly doing Cloud backups manually?
ME7 has a good video (which I used when filing my ticket). ME7's Video
https://www.youtube.com/watch?v=_15i959mGSw
It took several days to get a reply but eventually someone should get in touch with you in-game. Keep checking the Support section and when they have responded to you there will be 1 in a red circle on the Support button.
i did it few times already. guess what? nothing! still 99% of my progress is lost!
