didnt invoice me

didnt invoice me for work that was carried out 3 years ago. now is with holding papers because they didnt invoice, so apparently its my fault as i should be making payment without them invoicing me. wont respond to emails and when the md of the firm does he accuses me of making allegations without evidence when the evidence was supplied on the email he was responding too. lots of staff have left over the last 12months and service has dropped. recommended them to a friend and they wouldn’t reapond to his emails for weeks on end. won’t be recommending them anytime soon.