Hmmm Calming tablet, never had one of these with the 2 Root Canal's I've had.
I had a root canal done on the 29th Dec then 4 weeks later it was refilled, Before the Root Canal was done I had an old filling removed as my dentist thought maybe this was what was causing the pain $380 later for a new filling. Few weeks later I went back to say that I'm still having problems, at that stage a Root Canal was done at the price of $890 minus the $360 that I had paid a few weeks before to have the old filling removed and refilled, never had any probs with both of the root canals I've had.
I would go back to the dentist that did the orginal work on your tooth and talk it over with them, I think most certainly they should be made to either put it right or send you off to someone else that you will have abit more confidence in going too.
Good Luck