Service tax received later services exempted

An Management institute was providing educational services and charging service tax, later the Institute got affiliated with Mewar University ( A Deemed university) and now the services are Exempt. Now all courses are exempted from service tax. The problem is that Institute has already collected Registration Fees and 1^st Installment fees for the course along with Service Tax but the tax was not deposited with Department. Can institute reverse the service tax amount and credit to Fees a/c, by adjusting the same with future Installments ?  Please advice on the above matter.

Thanks in Advance !