Employer Payslip tax code incorrect

I registered the Government Gateway to check my current Employer Text Code which is 1257L, which I think is correct, but my payslip from my employer is a different one which is BR/0, I tried to contact my employer's HR Department, and they asked me to contact HMRC, but since there is no answer over the phone or I cannot reach any customer representative to answer the call. I am not sure how to inform HMRC to inform my employer to correct my tax code. Any advice?

Hi ,
 

If your employer is using an incorrect tax you will need to call Personal Taxes Helpline on 0300 200 3300.  They can arrange for a revised tax code to be issued to your employer.  They can also review your tax affairs to see if you have paid the correct amount of tax . Thank you .