If any of your ringers decide that ringing is not for them or they move away, you can simply log into your ‘manage ringers’ area, select the ringer and mark them as ‘lapsed’ (if they have given up) or disconnect from them (if they have moved away).
Their name will then disappear from your current list of ringers and will move to your list of past ringers. Their profile remains on SmART Ringer and they will still be able to log in and view their account at any time. If this ringer ever returns to ringing either at your tower or elsewhere, they can be ‘unlapsed’ them and/or reconnected to either you or another teacher.