BT ADSL v1.0 socket - can't remove faceplate

I have a BT ADSL v1.0 socket which I want to move. But I can't remove the faceplate to do so!
I've removed the screws and the left hand side opens. The right hand side opens a liitle at the top but the bottom right hand corner won't come away from the back part of the socket which is an old BT master socket. I've pushed in every direction, and tried to use a screwdriver blade as a lever in the gap between the faceplate and the back without success. It seems as if some sort of catch is holding it as there is a little movement but it won't come away. I don't want to do violence to it in case I cut off my broadband connection.
Can anyone suggest what I should do?

Where are you going to move the faceplate to?

As I said in my original post I want to move the *socket*. I can only remove the socket from the wall by removing the faceplate so that I can get at the screws fixing the socket to the wall. Once I have moved the socket I'll reattach the faceplate.

You can buy the whole thing with a filtered faceplate on ebay. You are supposed to pay for Openreach to move the master socket.

So, you are planning to move teh master.

There is just one answer to your question in that case. Get BT to do it -You are not permitted to move the master.

I didn't think it was the master, but is it the case that if the ADSL faceplate was put there it must be the master?

It may nit be teh incoming master, however, you did, in your opening post state that it is.

Apologies - you're right I did say that. However I don't really know. It seems to be the first socket that the cable entering the house comes to.
All I want to do is move the socket a few inches in order to change the skirting board it's fixed to. In the past I've successfully added an extension from that socket (before it had the ADSL faceplate needless to say). I would prefer to avoid paying a large sum for what's probably 5 minutes work once the faceplate was removed.

It could be voice extension wiring somehow pulled tight (if you have it and depending on its routing) and that prevents the removal of the filtered faceplate.

Fitted by BT back in the day, it IS the NTE.