I have MS Office 365 and Excel has been glitching out on my in SO many ways!

I have a MS 365 Subscription and have spend weeks trying to get help from Microsoft, spending anywhere from 45 minutes (before I'm randomly disconnected) to almost 6 HOURS waiting to speak to someone after I'm called back!?!? The list of the issues I'm having with Excel is ongoing ranging from it continually not giving me "permission" to save my worksheet, alerts telling me "reference isn't valid"when I try open a worksheet, sudden changes in permissions on my worksheet that I never made although, I'm the only one accessing them, and best of all going to open a worksheet only to find that ALL of the data that I spent a month collecting is GONE and different data from a new month was there instead???? I seriously have days where I think I'm going insane with this software and it doesn't help that I spend hours on end waiting to speak to someone but never end up getting anyone. I'm on hold right now as a matter of fact; this is the 5th time in 2 weeks that I'm trying. Does anyone know another way to get assistance? I've lost so much work time with these issues that I'm ready to cancel my subscription. I've been using Excel since 1991 but I'm at the end of my rope with all the issues.