They haven't the right to bully him, however it does sound like there is a 'history' here and it may bethatthe job and your DH are just not a good fit.
There are several issues here which, with my manager's hat on, I can see may be contributing:
- Not working Sundays. The shop is open on Sundays, so there was always going to be a need for staff. Unfortunately, there is no right to time off because of Church statutes, so this was only ever going to be an informal agreement, which they can revoke whenever they feel like it, unless his days of work are specified in his terms and conditions of employment. I take it they aren't?
What's likely happened is that the person who interviewed and agreed 'no Sundays' is NOT the person writing the roster week in and week out, so that's why he keeps being asked. Especially since, at weekends, staffing is harder because colleagues will have childcare issues, which DO have to be considered under the law. I'm afraid 'I don't work Sundays 'cause I was raised not to' wouldn't be cuttng much ice with me, particularly since he isn't even asking for sundays off to go to church. It does look very weak.
Please bear in mind here that you don't know the religious status of his colleagues, or his manager - how do you know one of them isn't also Catholic? Or Muslim? Or Jewish? Or whatever - lots of faiths have holy days. Vary few places of work will consider them.
- Toilet breaks. This is trickier - does you DH have a specified problem, or does he just 'need to go' lots? If it's the first, get it in writing from your GP and present it to work formally, with a covering letter. 'Explaining it' isn't the same as entering a medical condition onto an employee's record.
Consider here that this issue might be coming from co-workers, not management. Ten minutes toilet break every two hours in a (say) ten hour day is 50 mins (paid) break over and above what everyone else gets. If they're tannoying him to the shop floor then there's work to be done and he's been gone a while, so it might be that there have been complaints.
This is why your DH needs to get this on record as a genuine health issue, backed up. And then he needs to have a meeting whereby his working conditions are looked at to minimise the effect this is having on him and everyone else.
And, just by asking for the meeting, even if nothing comes from it, he's adding a heck of a lot of weight to his case should this situation really go south.
- Sickness. If he has a poor sickness record, then, yes, further sickness will be challenged. Dr's note, every time, and get it submitted ASAP. They haven't the right to ring him and threaten, but they do have the right to REASONABLY ask: what's wrong? how long do you think you'll be off? have you got a sick note? etc etc., particularly if he's gone sick either just before or just after a holiday. Make sure your DH is following his company's sickness reporting procedure at all times, because if those questions have been asked, either now or in the past, and they haven't been answered, some companies do resort to 'we won't pay you unless you.... whatever' They shouldn't, but if the alternative is formal disciplinary action, they will.
Again, the best course of action here is to see a GP and get, in writing, a statement of you DH health position. Submit it, with a covering letter, and ask for a meeting to clear the air.
Be aware that 'being off sick' is not a get out of jail free card. Unfortunately, if your DH is or has taken excessive time off, even for legitimate sickness, then his employer can decide that he's frustrating his contract and start disciplinary proceedures to terminate.
In your shoes, I'd be advising him to speak to his Dr and then take the whole thing to HR. Explain his side, present the evidence of bullying and ask that it be sorted out formally once and for all. As I said above, by doing this, he looks professional and proactive and that's a very good thing for him to look in this situation.
If they refuse, or they have the meeting but nothing changes, then he would have a strong case for constructive dismissal, should things deteriorate further.
Hope all that helps.