I ordered thai curry which was mentioned 199 they charged mein 298 with 5%gst and refused to pay my amount

I had ordered Thai Curry at Haldiram, where an offer price of Rs 199 was displayed on the table. However, I was charged as per the regular menu price of Rs 298 plus 5% GST, which came to Rs 313. When I pointed out the offer price at the time of billing, the staff took my phone number and assured me that the difference amount would be refunded to me later. I kept their contact number as well for follow up. Later, I received a call from them saying that the offer had ended and that they had removed it, and they refused to refund the difference amount as promised. I feel cheated as I was first promised a refund of the excess amount charged and now they are denying it. I request that Haldiram honour their promise and refund the difference between the offer price and the amount actually charged to me.