Lenovo — My power bank is not working properly

Address:

Bangalore, Karnataka

i purchased power bank ( lenevo pb410) now after 4 months its not working properly. problem is after charging for 8 hours its not even charging full smartphone of capacity 2200mamphere, so i kindly request u to assist me in this problem. i m not able to find service centres for aceesories, plz do assist me in this matter.It has warranty of 1 year so plz help me in refund or exchange of material.