Conference bridge and multi office after hours support

We are currently using Webex, Arkadin and a variety of other conference bridges and are paying too much for user accounts and call rates. We want to have: Conference facility: A conference facility with multiple rooms Users can either connect via inbound call, browser, or if in country dial number is not available request a call back Looking to have common features like seeing who is in the conference, inviting participants from within the conference room (email, Skype) Screen sharing would be good but not mandatory iOS and Android conference bridge apps would be nice if possible After hours support Our company currently provides after hours support from New York, London and Singapore to users across North and South America, UK, Europe, Middle East, Asia and Australia. We run after hours support shifts and also utilize an after hours telephone answering service. What we need to be able to do is use something like OpenVBX to: Take an inbound call or text Have call trees/patterns so the call will go to the designated support engineers cell phone via text (any of the above countries. Have no issues paying the international call/SMS rates of Twilio) For inbound SMS, Simultaneously post to twitter For inbound calls, if a voicemail is left, send SMS to next engineer and also post to twitter For all if the above, only want to use hosted services. AWS, Dreamhost or standing cloud. We already own a domain to use but will need to host this somewhere like the the afore mentioned. We simply don't have the time to learn and deploy ourselves. Looking to have project completed by the end of June. Also interested in using this as a replacement to our hosted PBX. Today we use vocolicity in the US and separate providers in other countries. All we own are phone numbers and Cisco handsets. This is a secondary project for us at the moment. Please reply with a his level SOW or overview. If you have done this before, great.