MTS data card speed problems

I am using mts datacard services for past 1 year. Recently I recharged my mts with rs1298. As mts promises high speed upto 3.1mbps for first 15gb, I recieved approx speed but as per plans, after 15gb data usage I should get speed upto 144kbps but I M getting speed upto 64kbps(8kbps,as 1b=8b),so I get a download speed of 8kbps instead of 18kbps from the last reset on 27/06/2012 also I complained several times for they are not helpful my mts no is 8518 kindly look into the matter and respond it would be very kind if mts can fulfill their services if not,kindly inform me there are many better services out there I would not like to waste my money on some bullshit services