Mpokket - Mpokket harrassment

I had taken a couple of loans and repaid from mpokket a couple of times and stopped using the app altogether about a year ago. But a few months back I received a call from them claiming that two loans of **** each haven't been paid and that the payment of **k is due although I had not taken the loans in the first place. Upon further inquiry they said that the loan was taken from my old device which I had lost over a year ago after which I had switched to a new device. They said that the issue will be investigated and upon further proof the payment will be discarded after which I recieved no further calls on the matter until recently when another employee of theirs started calling and have been harassing me to make me pay for a loan that was not taken by me. I asked for proof of the loan and all i recieved was a transaction number that I have no way of verifying. They have been harrassing me nonstop since then calling my relatives about the matter and blackmailing them and me telling me they will leave me denigrated to the point that no one will ever hire me in the future. They said that I had taken a loan on **th of August to a certain bank account and there is no history of such in my passbook history which I have taken a screenshot of.