Paying too much tax

Hi everyone, I've been paying too much tax as I can see it from my pay slip for no apparent reason. I've been working in the UK for almost 3 years, I had no issue at all during my first job where I stayed 1 year and a half. I have only one job but I've recently been changing jobs quite often, would that be a reason why I am paying too much tax? All my previous employers have let HMRC when I stopped working with them. I've been trying to contact HMRC but impossible to have them on the phone.

Hi,
Unfortunately we are unable to answer your query as it is not possible for us to check individual tax records on this forum. 
Please contact our Income Tax team using the link below for advice on your issue.
Income Tax: general enquiries
Thank you.