Employer's Wage declaration

we just found out that our employer for the last 3 months has declared to HMRC an amount £300.00 above what he payed us monthly. He has also changed the payslips from monthly to weekly when we told him he was short paying us every year. As I have some difficulties understanding some phone calls I was looking for an email to send proof of what we are saying. This is even affecting the Universal Credit Claim

Hi Paulo Dias,
Ask you employer to contact our Employer's Helpline on 0300 200 3200 for advice on rectifying this for you.
If they are unwilling to do so, you can send the documentation you wish to provide to
Pay As You Earn and Self Assessment,
HM Revenue and Customs,
BX9 1AS,
United Kingdom.
Alternatively, you can contact us by webchat via Income Tax: general enquiries
Thank you.