Airtel — airtel 4g hotspot device stopped working w. e. f. 16 august, 2018

I was given a 4ghotspot wifi device with a sim and after varification as per adharcard, i started using it w. E. F.25 jan.2018. It was working fine and its charges were paid in time all through. The sim is alright and is working with another simple airtel dongal. Since the device is not working, i am not being able to use 4g and wifi. This4g hotspot device may be changed.