Brook Street; wrong tax code overcharged on income tax?

I have been working through the agency Brook Street since November 2025 but recently looking at my payslips more carefully, I think I have been overcharged on income tax since starting. The HMRC app correctly has me down with the 1257L tax code but on my Brook Street payslips it has put me as 110T and 130T at different times. Working on 2 different BS assignments, I have earnt £12.36ph, £13.25ph and currently £12.71ph and am a full time 37hr/w worker. I should be on the basic rate paying about £45pw income tax, they have been charging me £70-100 odd!

I have contacted their payroll team to enquire (it's obviously a weekend so I don't expect an immediate response).

Have I been overpaying on tax? If yes, can I get this refunded? I have all of my weekly payslips from November 2025-present. If I have been overpaying on tax, it has been by about £40-50 per week since November (nearly 30 weeks ago), so an overpayment of roughly £1200!!

Looking for some insight and what people think