Job agency reduced pay for retrospective period

[Overwhelmedandunsure]

Hi,
just hoping for a few words of advice.
My son started a job with a local employer via an agency.
He signed a 12 week contract which detailed his hours and rate of pay.
He likes the job and has been told he’s doing well.
Four weeks after starting, and having had 3 weekly payments at the rate shown in his contract he received a 3 line text message saying there was a mistake in his hourly rate and as of a week ago ( which affects his next payment) his hourly rate will reduce.
I realise that as an agency worker he probably has few rights, and if they made a mistake I suppose they have the right to correct it for the future, which would at least give him the choice of carrying in or leaving.
It doesn’t seem acceptable to me to reduce his pay for a period he’s already worked. Is there any way to challenge this?
There doesn’t seem much point in a contract if it can be unilaterally altered retrospectively via a text message.
Rather irritatingly this was one of 3 jobs he was offered within a 2 day period, and he chose it partly because of the pay. It’s now reduced to less than the others.
Thanks

https://www.gov.uk/employment-agencies-and-businesses

I might suggest an email to the agency and the workplace saying he wont be in on Monday and be very clear about why

Its agency work. Tell him to see if the other jobs are still available.

Thank you for this link. It’s very helpful.

There's not a whole lot you can do moving forward - your son will need to decide if he enjoys it enough to take the pay cut. He can ask (and I'd ask the company, not the agency) if they'll honor the original salary if it's a deal breaker - but that may open a can of worms for them.

As for the money for the week he's already worked... I'm not sure where he'd stand legally. This is not an over payment where he's been paid more than he's contracted salary in error, which the company could legally claim back.

It feels like it could be an 'unlawful deduction', as they're paying him less than his contracted salary without his written agreement. Again though I'm not sure how this works with temp agencies.

If this was me, I would write to the agency to say that there has been no mistake with pay, and that my pay is as per contract, attaching a copy of the contract. I think if he pushes they won’t reduce it because of the written contract.

He has rights even as an agency worker. Unless the contract allows the agency to vary his pay rate unilaterally, the reduction is an unlawful deduction from wages. He should be clear with them that he expects to be paid as per his contract and that, if they fail to do so, he will be working under protest and may take legal action to recover the missing pay.

My experience of agency work was I always received terms of business including the place of employment hours, brief job description and crucially the rate of pay for the job, it also noted I had to submit a time sheet to confirm hours worked signed off by the company to receive pay. Has he not got a written contract detailing the terms?

Yes, he does have a written contract which shows his rate of pay.
The agency sent him a text message telling him it was incorrect and would be reduced from last week. The text came 3-4 weeks after he’d started and he has already been paid the contracted amount. He gets paid weekly.
He hasn’t been asked to sign a new contract.
He has spoken to the company where he works and they say the agency got it wrong, but he might be able to increase his pay if he does some additional training, which he’s happy to do.
I have suggested he speaks to the agency. I assume the company pays them more than they pay him, so maybe they can make up the shortfall for last week as it was their fault.
If they want him to sign a new contract at the lower amount from now onwards I don’t think he’ll have much choice as they could just get rid of him.