Alarm ringtone plays after calling
As per my comments:

Have you tried, as an experiment, to change you morning alarm ring tone to something else just to see if the same ringtone plays after a call. If not than it is not related to your alarms and may help you narrow it down.

Does this only happen if you have alarms set or does this happen even with no alarms set? Have you tried deleting all your alarms? If this works maybe try adding them back one by one. Please keep us updated.