Why 50 MB error occur while activating zero rental plan in airtel

Many users got an error while activating the zero rental plan on airtel, but now we have got reason of this error, today if you want to enjoy fully uncapped speed then you need to activate a small 3g pack, it can be zero rental plan, but when you activate it, by sending 3g to 121, or through any other means, it shows you that you have more than 50 MB data left, you can activate 3g plan only when you have less than 50 MB data left in your account. Now we are going to reveal the reason of it.
The reason is very much simple, once you have activated the zero rental plan, you cannot activate it twice.
Then question may come in your mind that why is not my speed uncapped, the reason is obvious, that trick may not be working for high speed, and server is demanding less speed from airtel, airtel then sends you less speed.
You can activate 0 rental plan by deactivating 3g then activating 3g services and selecting 0 rental plan from the list.

Overview and secret:-
You can never activate same plan twice a day that's why 50 MB error occurs. even you cannot activate Rs. 9 3g plan of 30 minutes twice a day, but when the plan data value is expired then only you can activate it twice but zero rental plan do not have any data value, so that's why it cannot be activated. Now if you get 2g speed in 3g trick and got 50 MB error, then automatically understand that it's not working in 3g mode.
I hope, you would be able to understand what's written above, for any queries contact nveenjain@gmail.com 
or comment below. I will reply as soon as possible.