Fawn,
Your display set is a
KX-T7433What we need is the system model number.
Probably a KX-TD 816/1232
You need a caller ID card in the actual system.
1 card is good for 4 incomming CO lines.
There is also some system programming involved.
Chances are that the prank calls will be blocked anyway so your really better off working with your provider.
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MrG