ABSA leave me alone

So another call today , one of many and the one that made my blood boil. I have a number of calls from ABSA trying to sell me or offer me things, ever time I tell them I am not interested and not to call me. I am already a client and just want to be left alone, they don't seem to get the message and just keep calling. I have now had enough and will be closing my personal and company banking accounts.