BPCL Domestic LPG — Delay in refill supply regarding

Address:

Coimbatore, Tamil Nadu

Sir,
We are having Domestic lpg connection of BPCL (consumer No:59692 ) in my name and getting supply from M/S Radha Gas Service at Thadagam road,Coimbatore.(Distributor code:114600).For the past six months we are not receiving refill as per schedule.The distributor says that we have to book the refill after 21 days from supply,and we will get the refill after 25 days from the date of booking.
We received last delivery on 23rd Feb 2012,Booked for Refill on 15th March 2012,So for we didn't receive refill the distributor daily giving different excuses from 7th April 2012.
We want to know that what is the actual duration between two refills,and what is the procedure for changing the distributor.Kindly arrange to do the needful for getting proper supply.

With Regards,
K.Surendra babu