Numbness even 6 months after hair transplant

It is best to contact your doctor about post issues.  Some patients may experience numbness on their scalp for a few months.  If a major nerve was cut during the procedure the numbness can be permanent. 

In hair transplant, the scalp tissue approximately gets cut 7000 times. This is why it is very common and normal to feel numb. This numbness period can go up to 6 months to 1 year.

At the time of the surgery, small nerves were cut that can cause persistent numbness that usually goes away by the 6th months. Be patient and it will eventually go away.  You did not state where your numbness is. If it is in the back of your head, major nerves lie there that could have been damaged at the time of the surgery