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.
NumberGroup provides business quality VoIP services to wholesale operators and SIP Trunk customers worldwide. We have over 1,000,000 UK and Internaiton telephone numbers are are a license UK operator with direct PSTN connectivity.