Sometimes there are some annoyed customers, so how do you think we can change an annoyed customer to a loyal customer to not shift to other competitor?

I give them the offers that suit them, and try to bring them in.

Bill Gates says “Your most unhappy customers are your greatest source of learning.”.

Offer him/her a seat ,Listen to them carefully, Note down their grievances one by one, Prioritize the problems one by one, may be some of them could be solved on spot and some will take time, so ask for time politely, take his contact number for future contact before he/she comes again.

The problem is not finished yet, analyse the problems, discuss with your immediate supervisor, suggest appropriate solutions.

Once the solution is final, do not waste time and Call him/her immediately, which will give the customers good gesture that the company gives importance to his/her problem.

I hope all these steps retain customers and most of the times most annoying customers becomes friends.