Try setting up a forum, and create a support section that is only available to paid users above a threshold. When your pathological customers try to email you c

Try setting up a forum, and create a support section that is only available to paid users above a threshold. When your pathological customers try to email you can nicely point towards your forum and say sorry, you are not the support team but they are welcome to ask questions on the proper forum. If they want to upgrade to access support, then you'll at least be making some money for your time. Use a private support email or token system if you can for your paid users. I've seen a company use Twilio and OpenVBX with a custom module, where paid customers get a number to access phone support, otherwise they get a voicemail saying 'buy support to call us'.