As far as I’m aware. You aren’t told why you are banned. Nor do you know if someone reported you. I think. If enough reports come in you may get a warning saying you’ve been reported a lot recently but the game never tells you that you have been reported, for every single report that comes in.
Now, as the other guy said. Sharing accounts isn’t allowed we believe. I need to personally read up on this so take it with a grain of salt but. Even though she/he gave the account to you. Its still sharing. Oh and, this is just me but, the accounts. Don’t they all belong to Blizzard?
I’m pretty sure they do and we only have a “license” to use the accounts.
And last time I checked, though I can be wrong here, you aren’t allowed to share or give away what isn’t yours to begin with.
As for your previous suspension. I doubt a vpn would cause a ban.
You can as the others stated, to contact support but don’t get your hopes up in finding out why exactly the ban came. As they don’t have to share that information.