Decrease in tata photon + speed after 7 gb usage

I have been using tata photon + since last 2 years. I have 5 gb + unlimited plan @ rs 950/Month. Earlier speed used to be 155 kbps after 5 gb usage but now they have imposed 1 more condition I.E. From 5gb to 7 gb speed is 155kbps and after 7 gb usage speed of tata photon + reduces to upto 32 kbps which is totally unacceptable. No where they have mentioned this condition in their plan and speed becomes so slow that even email pages don't open up. This condition is not acceptable which limits device usage to 7 gb data only whereas it is so called unlimited plan. How can they impose such a condition afterwards for old customers??this is pure cheating by tata.