We recommend Artie. He tuned our piano, changed a broken string, fixed a couple of sticky keys and one of the pedals of our piano. Very friendly and approachable. Here's his number: 0501223260
Hopefully these might be of help.
http://www.houseofpianos-uae.com/tuning
This place is in JLT. They sell everything from guitars, drums and keyboards etc..They might have someone they can recommend.
http://www.musicianssupplydubai.com/contact-us/