Airtel Landline — a payment clause

I have been paying my Airtel landline bills punctually on the due date by cheque for who knows how long. Now I find out from their customer care that if you make a payment by cheque the money is not considered paid till it reaches their account (i.e. you have to pay by cheque 2 to 3 days before the last date of payment) and you are considered a defaulter and charged Rs.75 for late payment every next bill every month. Multiply this by the million people who do not know this. I am not sure but in every other product, when you are given a last date, it means pay by cash or any other banking instrument. Apart from this they do not give receipts, even if you ask, so the executives cannot tell what is at stake. It may be mentioned somewhere in their 100+ terms where I did not notice it but in many other companies, executives give receipts and voluntarily tell you what is involved. Even the Airtel person tried to cover up this pinching of money by saying, they cannot tell if I will be penalized till the next bill and I was lucky to get the answer out of him. So I cannot agree that Airtel provides honest and the best services. But I have to stay anonymous as I still have to use their phone.