To be fair you can't really complain that you are paying for a service you are not receiving just because you chose to remove the phone sockets in your house - This is not Virgin's fault or responsibility.
In fact, you should not have removed either the BT or Virgin master phone socket at all as this belongs to the service provider and is the demarkation point between the internal wiring (your responsibility) and the service provider's network (their responsibility).
It wouldn't surprise me if (quite rightly so) Virgin charge you a fee to come out and rectify the fault you created.
Are you able to confirm that you have removed the BT sockets only or the virgin media ones that would have been installed when you sighed up with us, I ask this because the virgin media and BT sockets are completely different, If the virgin media sockets are still there please connect your telephone into the wall socket and tell us if there is a dial tone.
I appreciate that you mother in law's phone plugs directly into the hub, however although we do offer this landline method it only when you have been installed that way. I have double checked your details, It is showing that your landline services is being provided though the wall socket as @Gaz82 has mentioned, if you want the landline services though the hub you would need an engineer out and there maybe a charge if there is no fault.