Airtel - Bill amount not adjusted

On **.**.****, I changed my two airtel numbers from prepaid to postpaid. The numbers are as follows:
*. **********
*. **********
Both numbers were recharged with prepaid plans. For the first number,i.e. **********, recharge was done **.**.**** only with the plan of Rs. ***. For the second one, i.e. **********, recharge was done a month ago with the plan of Rs ***.
Since I upgraded both my numbers into postpaid plan, I could not use the benefits of those plans with which I recharged my numbers, especially, on the first number.
The money has been credited to company account. Thus, I request them to adjust the amount of those prepaid plans in my upcoming bill. I chose family plan for these numbers.
The same adjustment was done by vodafone company as well when I upgraded my prepaid number to postpaid. At that time it was a matter of only ** rupees. Still they adjusted without bothering me. Here I recharged with big amount which has been credited to airtel company's account. Still the company is not ready to adjust this amount. While changing from prepaid to postpaid, their employee did not give any information regarding this.
During this pandemic, I am already suffering a reduction in salary. Now this company is also looted me.
I expected a good quality services from the company and timely resolutions.
I mailed them all the details on their mail ID ***@in.airtel.com on **.**.****. I waited for their response. Its written on their website tgat they provide **×* customer help, however this didn't happen. Then I took it to twitter. And posted my complain over there. They said they'll call at my preferred time. But they dudn't. And sent a text that I did't respond to their call. I told them that I didn't receive any call and I was waiting for it. Then I gave another time to them. They called this time and said that they have different accounts for prepaid and postpaid, hence they can not adjust this amount. I found it very illogical. Whether prepaid or postpaid, the amount us credited to same company. Then how they can't adjust it. They wasted my time on call. This response they could have written on social media so tgat everybody get to know their ways of doing fraud with people. Kindly look into this matter and help me in this.