Prevent Dial UP connection from exitting if abort seq was sent

[zvada]

We are trying to make an Dial Up connection with a mobile phone using a self programmed logging tool (something like hyper terminal)…
I have now to find out the abort sequence ( = call prefix string???) we have to send to the mobile/modem to exit the data mode.
Or on the other hand – we need to program the logging tool to prevent the modem from exiting the transfer/data mode to the command mode if the sequence is send (e.g. if the sequence is included in the data which is sent trough the modem).

Any help (internet link, code…) would be great