Some halls provide a standard BT phone line which you are at liberty to have connected yourself. Disadvantages of this are being tied to a contract period and that you can't call internally. Advantages however are that you can enjoy paying decent rates for calls and can get unmetered dialup or ADSL if it's in your area.Speaking of telephones and broadband internet, I've heard that some places have very restricted internet access (ie. certain ports, protocols and sites blocked/filtered) and telephones that charge a fortune for incoming and outgoing calls.
Most halls however have some god forsaken internal phone system which charges ridiculous rates for outgoing calls, ridiculous rates for people calling you, and usually you have no way of getting unmetered internet access from them. The internet access in particular can be a problem since not everywhere has network access.
In my time whilst there were policies to prevent you from using filesharing software and messenger programs on the uni's own computers, you were perfectly at liberty to do whatever the hell you wanted on your own, even though you were using a university connection, I understand now though that Plymouth have restricted your access somewhat, something I believe is becoming increasingly commonplace.