Xolo — contacts loading very slow

Address:

Dibrugarh, Assam, 786001

My phone xolo era 1x tooks about 7-10 mins to load the contacts, why?
Whenever i want to call someone i have to wait for a long time to call.
So, please give me a solution to get rid of this problem..
This problem has beenoccuring in my phone from the beginning.
The contacts got totally vanished sometimes while using whatsapp.
Maybe this problem doesn't occur in other xolo era 1x model.
So, please help me..