Alternatives to IPLC

Well I am an MBA doing a project for an call centre organization in Ahmedabad. I want to know who are the call centers in India using IP based like VOIP or MPLS based connection to make their calls. The company is now making calls through IPLC based connection which seems to be quite expensive for them .What are the alternatives available and how good will be a MPLS based connection for a call centre.Expecting a reply .