Yea, I'd understand the frustration if OP was paying for the service, but this reeks of entitlement. If you are a free user don't be mad when the company tries to convert you to a paid user.
A better example is how pushy Apple is with upselling their iCloud plans. I opened my laptop the other day and it auto-opened the iCloud settings app with the more expensive plan pre-checked.
Dropbox makes constant notifications on your desktop about upgrading alongside emails. I'd have considered paying for them if they weren't like this but now I never will. Maybe they'd have an easier time being profitable if they didn't push away all their long term users.
A better example is how pushy Apple is with upselling their iCloud plans. I opened my laptop the other day and it auto-opened the iCloud settings app with the more expensive plan pre-checked.