Previous employer not providing wage slip

I worked for someone for two and a half weeks last month.

When i took the job, it was always intended to be long term, alongside my studies at University.

However, when I received my University timetable it became clear that I would not be able to continue with the job as the hours would clash.

I therefore reluctantly gave up the job. The employer tried to claim I had to give notice, but I had already signed a contract, in which stated no notice was required by me if I was employed for less than four weeks.

I was then given a cheque, which is about £50 less than it should have been for the hours I worked. The cheque was for a round amount, which I found suspicious, as my hourly pay was not a round amount.

I texted the employer to ask them to provide me with a wage slip so I can see the breakdown as to how the figure I received was arrived at. No reply.

I have sent a further 4 texts since then - still no reply.

No responses to my texts is making me even more suspicious that something underhand has happened here.

What can I do to resolve this? I am aware that I am entitled to a wage slip by law.