Today I've received multiple (at least 20) repeats of the same message at 10 minute intervals. So I checked if I can amend the service. You can do so by calling 0800 587 5252 and following the menus. Choices are about 'curfew' which restricts the calls to certain times of the day (actually more times of the night) or simply turn the service off completely. I chose the latter. Someone else might find this a useful tip.