No, we do not provide internet service as a part of our plans.
Our data center has a fast connection to all major Singapore ISPs, you would have no problems with speed or reliability.
A call would require 100kbps bandwidth (or 0.1 Mbps), so if you would expect 100 users to do calls at the same time, you must allocate 0.1 Mbps x 100 = 10Mbps bandwidth to be assigned for VoIP traffic.