Tax return

firsttimebuy1

Hi,
I went to start my tax return last night so I knew how much I would need to pay. I was classed as self employed from April 2019 until end of July 2019 so 4 months, as the company I was working for gave me a permanent contract beginning August 1st 2019. 

Now,  when I'm doing my tax return it has my tax information from my employment August 2019 - April 2020, and I fill out my self employed part after this section, I filled it out as best as I could but when it comes to the calculation at the end of what I owe, its showing as £1750 which is alot more than I expected as when I submitted my return for 18/19 it was less than half that amount. 

Its including £570 to pay for the tax year 20/21 aswell but I told HMRC that I was no longer self employed when I got my contract last August, so unsure why it's still saying what I will have to pay forward for 20/21 aswell.

Do I pay the amount altogether with what its showing for 20/21 and then get a tax refund or do i need to ring HMRC for them to amend the total?

Thanks