Consumer Redressal

Sir I have an MTS prepaid connection. My last recharge was on 23 Jun and as always is the case with MTS the speed reduced within a week. I contacted Customer care-MTS, for remedy. They advised me to recharge, which was done on 14 Jul. The speed did not improve and now when contacted the Customer care says that my speed will not improve till 23 Jul as my previous recharge date is valid till then. They also say that since I have recharged on 14 Jul my validity date will now onward be on 13th of every month. Now I have lost ten days from my validity period and I am deprived of the speed that was promised after recharge. Kindly advise if this is legal.