why do i get asked to pay more, every time i use it. ive been subscribed for years paying for premium , and never used as it asks me to pay more.?

There isn’t much to work with: In what way is it asking for more - Is it offering more programs or services, etc. ?

Is it happening after an Avast scan or other action ?
Check out your AvastUI > Menu > Settings > General > Personal Privacy: In particularly the Offers option, if that is enabled, uncheck that and see if there is an impact.
Avast-Personal-Privacy-Offers