Advice on UK Visiting Visa

Hello there,

I applied for UK visiting Visa in August 2018 at a visa application center, because am not in my home country, and later sent my documents including my passport to the UK embassy. Receipt of my documents was confirmed by the Embassy early September but till (December 2018) now my passport hasn't return.

I messaged the Immigration office and I was told i will be contacted in 15working days which elapsed last Tuesday. I sent any email to them and i was told to remain patient but they can't give any timeline for the return of my documents.

Am really confused. Has anyone experienced this? What should be my next step?

Your advise will be appreciated, thanks.