Should post faster
As a contractor your company is providing services to your client, so you personally cannot have a "job title" as you do not have a "job" within your clients organisation. Your company is not supplying labour to your client, it is providing services. When dealing with agents etc, most will give a job title as a useful way to describe the work that is required but after this point you should pretty much ignore it. Use whatever title your client wants you to use (within reason of course, if they start calling you tuliphead and want you to use that title in your emails you should refuse).
I live on CUK
Nice But Dim
Contractor Among Contractors
Where there's muck there's brass.