Custom PBX Development - preferrably cloud based

I am looking to build a Custom hosted PBX system for my adult hotline. As it is not the typical pay-per-call setup (it's not an adult chat line ad thee is NEVER any connection to a live agent; it is a 100% pre-recorded automated adult directory - of sorts) I cannot go the usual 900 number route. Specifically, I am looking for a PBX 800 number that charges me (my company) a flat per-call rate (like any other toll-free number), making it free to call, but has a payment system attached to it (or can easily work in tandem with a payment system) so that when it is time to direct callers to the "payment menu" they can then select from a list of "fixed" prices (i.e. pressing 6 on the phone will ALWAYS correspond to a $49.99 dollar charge, making it much easier to calculate than per-minute billing) and they can then use their credit/debit cards to make payment. I will make profit off the paid advertisers (the strip clubs, massage parlors etc.) who pay to advertise on the hotline. This means that I will need to allow callers - once they've paid - to be able to leave a voice recording (their 'promotional ad' which can have background music etc.) that can then be uploaded to and heard on the hotline by other callers. There is a bit more to it, as the PBX system is data-based, and will run off a database (the back-end office where uploaded voice ads will be placed in 'queue' in the various categories, and when there is no more space under that category it works just like a 'this mailbox is full' kind of thing), but this is the short explanation of what I need. I can find a PBX developer, no problem, just not one willing to build this kind of thing for "adult entertainment" purposes, so please let me know if you can help. Thank you