Ambrane India — ambrane power bank is not working properly after repairing

I have purchased ambrane power bank 10k model no. Pp-111-on 03 oct 2019. After using 4 month, it's charging capacity become very poor.
Now it can charge hardy one time of 4k. Battery after full charge.
I contacted with service center, they told me it takes 45-50 day for repairing, bcz it repairs only in delhi.
After approx 40 days i got my power bank back but i was shocked bcz ther was no improvement in it charging capacity, they have returned me same product without repair. And it's performance was less than the earlier.
I am very disappointed to ambrane service pls give some attention to these problem.