Credit card harassment

So I am facing this incident currently. I made a payment of my credit card dues through Paytm but the bank tells me that they have not received the payment. I showed them the payment history and with the discussions concluded that the payment was a success but on the billed desk platform it might got failed due to some technical error. My total bill is of value 52000. They have appointed their collection agent and he is continuously calling me and texting me on WhatsApp to make a new payment because the older one will get credited back either to my account or on my card. I am a salaried person and belong to a middle class family with a salary of 30-32k per month. To make a payment of 52k it was a very difficult task for me because I have other loans too that I have repay them on time. So he is harassing me daily to make a new payment. Usually payment takes 2-3 banking days to reflect back in the account or get credited on the card. It’s been 4 days nothing has happened. What should I do in this case.