It depends on what equipment is at the office and with you. If the VSAT is accessible at the office through a LAN and a dial-up modem is also connected to the LAN by whatever means available, or if the VSAT equipment itself handles such a connection, then you should be able to connect by telephone. -- Tom
I presume the VSAT is providing internet for the office. These VSAT internet connections usually have fixed IP addresses, so you connect to it like any other Internet resource. This is based on the premise that the office services, such as e-mail or FTP server, are made available through whatever firewall is used at that office between the LAN and the VST access. There is not usually any need for special equipment other than the VSAT modem/router.
Please note that VPN connections do not usually work very well over VSAT, due to the signal delays screwing up the TCP timers inside the encrypted packet.