Marks and Spencer London - No refund of money

I have ordered sandels and white top from marks and Spencer. The orders number is ********** and **********. I have paid Rs **** and Rs **** and two different times but lated I retured the product because of the size issues, but untill now I never got my money back. I have mailed them multiple times regarding this issue and also called million times, but they are repeating the same thing that they have initiated the refund and keep sharing the reference number. They argue that I should talk to my bank and I told them that I have consulted my bank in last three months for multiple number of times, but their is no issue for my end. I never expected this kind of experience from marks and Spencer, which is such a reputed company. They have harassed me so much and have economically and emotionally dreained me. I think it's very wrong on my part to get harassed so badly for my own money. I am a student and have been facing crisis for such a long time and I am heavily disappointed in marks and Spencer.