Apple India — slowing down of iphone 6

Address: 152001

On updation of my software from ios10 to ios 11, my iphone6 has been slowed down to much extent. The phone just stuck in between the calls and hang again and again. Touch got irresponsive.
This is not fair for apple to slow down previous versions.
Imei [protected]
The problems just continued even on resetting my phone settings
I will have to proceed legally if no reply or solution will be provided to me. Also i will publish the same in newspaper giving them an affidavit for the problem.
This is not good for a highly reputed company to do such activities