I can easily access VPN account with Huawei MTX880 modem.
Shiro modem sucks as it does not allow VPN connections.
There is another modem of Huawei i.e. HG510 I guess. I am unable to access VPN account through that as well.
Any guide or idea about how to use VPN with different modems. Any specific modem setting or it has something to do with account settings at PTCL end.