MCent — i was given 50% discount but when i completed my coin to recharge they reduce it by 25%

When i installed the app i was given 50% discount on recharge, but when i completed coin for recharge they reduces it by 25% and need much more coin to recharge. This is not fair.. It is really fake and makes negative reviews for the users if i don't avail my previous plan then i never say anyone to use mcent and never share because it shows the plan after installing then after reaches the point they changes in plan... This is really irritating for anyone so i want to mcent if it shows any plan after installing not change until one time not recharged is happen... Otherwise i uninstall the app...