Different types of communication and when to use them. How to deal with a customer complaint

I have been delivering Customer service for over 20 years in a variety of sectors and industries in the UK. I have successfully supported the Level 2 and Level 3 Apprenticeship Program- an example of some of the companies are :- Avanta ( was Virgin Trains) Silent night BMP Parabis Bank Bank of America Head office - Chester MOD army bases A variety of Navy bases Mitie call centre G4S security officers within the job centre. I have delivered support on a variety of programs and also bespoke to meet the customers individual needs. This has enabled some of them to move up in the business and gain promotion with the training given.