I think I would just be factual to the amount of pain you are having and the historical information on the change of medication and the date. I would then "ask" the Dr if perhaps there could have been a conversion issue since I was still having so much pain. An educated Dr would, as you said, know the proper conversion.
You certainly don't want to go in to see a new PM and bash the old one. It won't get you anywhere, that's for sure. If you just give a history and a summation of the pain you have been having since the change, it may help put you in a good light. The Dr should immediately know why there is an issue when you tell him/her. If not, then you can go on from there. It's just my 2 cents, but coming on too strong on a first visit with a new Dr doesn't always work out as well as we expect. Sometimes they will even turn us away because they may consider us "problem" patients and I don't want that to happen to you. Your chart should validate everything you are saying and I'm sure the Dr will take the time to look it over when you mention the med change, even if they haven't had time before the apt to do a close evaluation.
Best of luck!
Failed fusion L5-S1, Pituatary damage, HGH Def, Fibro, Bladder surgery failure, Nissen Failure, GERD, OCPD, GAD, MDD, CTS (Bilateral Surgery completed), CFS, TMJ, Migraines, Vit D, A, Magnesium, deficiency, HBP, Idiopatic Reactive Hypoglycemia, serious Edema, too many Drug/Food allergies, sensitivites, and current meds to list.