Help with non contractual terms

[Whoppery6k]

Good afternoon, it's been quite some time since I last posted but once again I'm looking for advice.
I've been with my current employer now, for almost 4 years.
I occupy a senior managerial role, in a busy retail store.
During these 4 years, I have constantly been plagued with late-night callouts for our alarm systems.
These have been highlighted as faulty on numerous occasions.
Sometimes I can be out three or 4 times of an evening for the same fault.
While my manager direct completely agrees that this is a gross misuse of time.
His manager, and the company's loss prevention insist that every alarm call must be attended regardless.
I would say in almost 4 years I have attended or well over 200 alarm calls.
So far none of which has ever been anything other than a fault.
Last year it was agreed that the 3 other members of management in the store would now share the burden, so we take it in turns with each other having one week on alarm calls.
I can't think of many occasions off the top of my head in which one of us has not had to attend an alarm call during there week of being on call. some of these have included Christmas Day.
2-weeks ago while in the bath I missed an alarm call, this missed call carried through the chain of managers who were each busy (Two of which were on holiday) before going to the area manager.
They have now informed us that we are not to take it in turns on alarm call all and we must be readily available every evening to attend should the systems go off.
So if one of us should be busy, the other three are on standby to attend.
We received no extra money for this service, and have just become aware it's not actually in our contract, it does form part of our job description according to the company website.
All four members of management are on salary and any hours used to attend alarm calls we may take back in our working week.
As a company any hours worked over contract hours are not paid but should we be under contract hours during a week we will not be paid for those missed hours.
Having spoken to to the other management members we are considering saying no more to the alarm calls.
We don't think it's fair being on call 365 days a year.
While yes we get the hours back it doesn't take away from the fact I am up at 2 in the morning attending an alarm call call all that I know is faulty.(I may have been out twice that night to it already and we are told the fault code over the phone)
The faults have been highlighted more times than I can count but the company refuse to replace the alarm systems due to cost or even have them properly repaired.
So my obvious question is where do we stand should we now refuse to continue this practice.

thank you in advance as always

[ULA]

You say that being on call to deal with alarms at the retail location out of hours is not part of your contract but you mention a job description on the website, is this one that has been given to
you directly at any point?

Have you individually, or as a group, thought about raising a grievance regarding how the call out system is worked including raising the quality of the alarm system?

[echat11]

Excellent advice there, employee unity and raise a grievance. Your employee handbook will tell you who you can complaint to up to Director level. If the alarm system was functioning correctly it wouldn't be going off that number of times. If the management / company knows that it's going off that number of times and they are asking you to attend, that's ridiculous.

Someone at Head Office needs to figure out why it's going off so much, is it too sensitive to activity i.e. sensors on windows, goes off slightest touch, vibrations etc.