Sounds like they are not good at supervision, only at what needs improvement and not in telling you what you are doing right or well. Remember, people who have done stuff a long time know how to do it and forget what it is like to not know how to to do.

I would go back to the job centre and see if you can talk to one of the same persons you talked to before, tell them you don't think this job is working out so well, you do not like it and seem to be getting a lot of criticism, do they have any other jobs you might qualify for that have a little less customer service (stock clerk might be good or a job in a library (lots of public organizations have libraries too, like large law firms, etc.) or file clerk perhaps, something like that).