@ Muhammad: No use mate. We have mutual relatives and it'll be very easy for him to acquire our new numbers as well.
@ techn: I did add him to a reject list using a phone blocking app, but it still sends in the call. However, the bigger problem is that I can't stop him from messaging or bothering us at 3 am on our landline. Also, I can't be bothered to stoop down to his level by using his language on him :S
@ doha estate: Interpol in Doha? I have seen their office near ParcoMall, but would they be able to help with such a complaint?
@Molten Metal: I think he resides in Al-Ain now. Can I still contact the UAE police and launch a complaint against him? Any specific website you would recommend buddy?

@all: thanks a bunch for the advice, will try and let you know if it works out.