FNB engaging in anti competitive behaviour

FNB is engaging in anti competitive behaviour. I have attempted to close my account numerous times. In all those instances I spoke to someone from head office who assured me that it will be done within 48 hours and then nothing happened. I received a very competitive offer from Investec which includes my home loan. I have been attempting to close my FNB accounts to no avail. I asked Investec to assist but they aren't able to. Dear FNB: is it legal to engage in this anti competitive behaviour and force customers to stay with you. Customers should not stay with a business because they are coerced by because they see value in the business' offerings.