The sad but true answer in NO. You can't disconnect the embedded viaccess cam. (I have the same problem)
The problem is that with viaccess the the 9800 reverts to the embedded viaccess cam and won't look further.
The MM +9800 should work on some channels but sometimes needs a reset.
What channels are you trying to watch ?
Some TPS channels can be made to work by fooling the decoder by first selecting a channel like BBC Prime (TPS) then selecting a FTA channel, waiting 3 secs then going back to BBC Prime. Works for some of TPS.
But each time you change channel you must do this.