Iphone 7 shutdown problem

I have buyed this refurbished 6 months or more not accurate. My iphone battery health is 100% my battery is change by the refurbished seller from which i have bought my iphone . Yes i can you it in plugged but it gives me a lot of trouble using. In plugged it get more restarts than non plugged. Sorry my

English is bad😌

Yes i now it is not refurbished by apple i have buyed from cashify it is quite famous in india i also buyed from them.

the 6 month warranty is over which was given by the seller. I having problem which i think it is hardware problem