Nokia India — service centre

I had recently purchased a nokia 7 from darrang cycle, tezpur, sonitpur assam on 19/06/2018.. Product serial no.- [protected] / 86.
I had financed it with hdfc ergo general insurance co. Ltd. And got the extended warranty insurance done with them.
After sometime my sim goy stuck and i couldn't open the sim tray, so i approached them and they sent the mobile to "system solution", tezpur for repair. I was initially asked to pay 1600/- for the repair, but finally they settled for 1000/-.
Now, first of all, i would like to know whether they should have been charging me for this (Since it is under warranty period)
If yes, then for such a small repair, don't you think they have charged me too much and exploited my situation.
I would request you to look into the matter and take necessary action against your service centres which are actually taking undue advantage of customers like us.
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