No, finding an ad is a random process that you can't control, so 'finding an ad to unsubscribe' would be a complex process.
Instead if subscribing is done through an online form, so should be unsubscribing.
If subscribing requires calling a phone number and being put on hold for 60 minutes and then having a person on the line trying to convince you to _not_ subscribe to this service, then if taking this literally unsubscribing is also allowed to involve calling a phone number and being put on hold for 60 minutes and then have a person try to convince you to not unsubscribe.
Instead if subscribing is done through an online form, so should be unsubscribing.
If subscribing requires calling a phone number and being put on hold for 60 minutes and then having a person on the line trying to convince you to _not_ subscribe to this service, then if taking this literally unsubscribing is also allowed to involve calling a phone number and being put on hold for 60 minutes and then have a person try to convince you to not unsubscribe.