For one time advertising promotions or typical requests it is easier to use services of the outsourced call center. Main advantage of such a service is that the company who rents it is free from the necessity of keeping the operators and organizing their work flow.
From mobiSIP Android or iPhone: SIP Client iPhone is uniquely designed and developed to add the power of making voice over internet transfer protocol calls directly through the Android or iPhone. It’s developed by mobisnow.