Before you switch, be aware that alarms do not work reliably with VOIP (internet phone) or with Magic Jack. You must have a land line or cable for signals to reach the monitoring station. If you only have VOIP, than you will require a GSM (cellular) communicator which results in slightly more costly monitoring than monitoring on a regular phone line.
If you are switching from one Phone Company to another (Bell or Cable) the new company must make their connection at the same demarcation point as your original phone line. Please take a moment to test your alarm with the monitoring station before the phone tech leaves your premises and make sure the test signals were received at the station.