Illegal interest

Hi Sir, I am so harnessed about the builder unwanted demand.we have paid all the amount (100% +All the allied Charges) when we are asking for possession letter from builder they said some signature left from builder,They wasted our one month and last week we had called for possession letter.they are demanding and told us that some interest amount is left from your side we were shocked.As you are already aware about from date of allotment buyer need to pay the 40% amount within 45 days.we had apply for home loan, due to some issues(NGT) from builder side and bank had arise some issues on home loan we were worried on that time if the days are more than 45. builder will charged interest amount from us but and we had discussed with builder ha said no worries we will take care.and now after one year they are asking for that delayed interst amount on that time bank released the loan to builder account one week late due to builder property issues(NGT- National Green Tribunal) from our side all the papers were submitted on time . "So here my question is if there had been delayed from builder side due to (NGT issues)bank released loan one week delayed who will be responsible to pay the interest 24% on property. as they are asking this interest amount from us. so could some one please help me that is there any kind of law which can help us and give us a relief from this mental harassment.