there are a few mechanics in Karachi who repair auto boxes, they are scattered around, the oldest of the bunch are near Khudadad colony and PECHS.
It is mandatory to use brand new friction parts (discs and bands) and seals and replace any worn metal parts too - the reaction pistons for the bands should be inspected and replaced if showing signs of cracking or wear.
before any of this - make sure that you have an automatic transmission ECU in your car and that the select lever is working correct.