need a multi tenant pbx sytem setup with website

i need a multi tenant system setup where i can sel pbx and multi extensions to my clients, they need to be able sign in and change up date there own acct. need billing system where they can pay for pbx did numbers and talk time(please give me your suggestions). i also need a call back feature set for each pbx extention i set up(so i will need to know how to duplicate)also will need to have the did number show up in caller id for the call back feature(so customer will call system then dial out thru there ext and have there number show to who they are calling) free pbx or elastix are preferred,but willing to learn new software. i am not sure if i will need hosting however i will need to have the ability to create 500 extentions with there own sign in in the [login to view URL] if i need certaain hosting capabilities please tell me what i will need to host my self or using a hosting company the specs i will need in your response if that is not there i will not need your bid. will also need to be instructed on how to set up sip phones and soft phones will be using polycom 330 if this is beyond what you want to do please do not bid. will need suggestions on carriers for reliable did service and did purchase for less than a 1.00 per did and unlimited talk in and outgoing for very good rates preferable 5.00 or less if any of these things are out of your realm please do not bid. by the way i am look at 10 day turn around at max for project. also i here there is a software that can do what i need for 1500 if you think that is a better option and you can train me on it i will pay for that as a seperate job. will need a site to conect to this hook up for billing and order purposes so if can do please let me know in response i am willing to split with another free lancer