I had a similar issue with just using my account altogether after it had been shut down (They said it was suspicious activity but I suspect it was my using Synology's sync feature instead of their OneDrive sync feature). During the shut down, my files weren't syncing at all and they didn't give me access to any of my files (fortunatly it was only the backups).
I could only email customer service and in the span of like a slow 10 days, I asked about 10 times what suspicious activity existed and why I hadn't been given any notice about a security issue and then why I hand't gotten a notice that my account had been shut down. They only had one customer service agent respond and he played it out like he either didn't understand what I was asking or responded to a different question - never responded. I asked like 6 times to either speak to another agent or his manager and he played the same game.
At the end of the exchange, I emailed him to say OK I'm going to take it that you're refusing to connect me to your manager to complain about your service and refusing to respond to questions about security issues on my account. I think if you give people the run around for so long, anyone else would feel the same way. After that he responded that I was the only person with the security issue and that because of that there wasn't a need to investigate further.
Not a good experience. Sucks that a paid a year for 365. Will only mean I have a good amount of time to find something else.