FNB terminate bank accounts

Received an email from FNB requesting Updated FICA information, a day later received another email that FNB wishes hereby to terminate my accounts and close my account with them. I made contact requesting on what grounds they wishes to close my personal account, they couldn't given me a straight answer. I then went into the branch which the branch has been trying and escalating this matter but yet FNB is still wanting to close my account. There has been no ******* activities happening, I want to have a solid answer to why they wish to close my accounts. Even the branch cannot help one to save the accounts even all FICA has been submitted. This is totally wrong. Something is just not sitting well with me in regards to this.