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.
Citel Technologies , A Voice over IP Phone company that provides VoIP Business Phone Systems. Its Main products include EXTender, PBXgateway, Upgraded Hardware Products, PBX platforms etc.