If you were injured at work, of course they want want either their own doctor or Occupational Health to see you.
I'm not entirely certain but believe they may also have a legal obligation to (but this may be dependant on the severity etc).
I know when I was off longterm sick a couple of years ago, my employers asked me to attend an appointment with their chosen doctor; even though I was under the care of my own GP, NHS physio & neuro team at the hospital. It meant HE could refer me for an extended course of treatment with a private physio; that they paid for.
Before discussing a return to work with you, they need professional advice on when & what you will be capable of. Also, if the injury was an accident or caused due to negligence on your, their or someone else's part, OH get involved to assist in implementing safe practice etc.
I know the thought of going is horrendous (many a time I could have quite happily not gone, knowing I'd come out feeling like I'd been hit by a bus!) but if you CAN make it, I'd really recommend you go.
Definitely give them a call and explain your difficulties in attending, they may be able to change appointment time to something more convenient if it means someone else can drive you etc but I don't imagine they'd agree to ONLY a telephone consultation.
I do hope your pain lessens soon
for you.