Cell phone / tablets with SIM data connection get unique IP address for the session duration. It remains with the service provider logs with respect to cell number, sim IMSI & device IMEI number. making electronic banking 'a bit' safe. This is reason of your success on Cell network.
while the PTCL services are pathetic across the board electronic banking / secure services / encrypted mail server connection usually fails when PTCL BB is used. PTCL BB dns gateway changes at random hours there by the IP address change while connected which result in abrupt session termination over SSL secure websites.