Termination of bank relationship

I've received a letter from FNB wherin they state they will cancel my accounts. The letter does not mention as to why they are doing it and there is only an email address, no contact numbers and I had to quote a ***. When I emailed them with the query they sent me the same letter. After banking for 8 years with them and not being informed as to why they are doing this is very unprofessional. I would like for them to contact me on *** as to why they are doing this.