Poor service from Isa

Mtn customer service is absolutely ridiculous, I called to follow up on my query after being assisted the week prior and also being told to call back, the lady named Isa was extremely rude and had no way of speaking, even after explaining the situation she stills gives out numbers that don't exist for me to call for assistance, eventually after having such a bad attitude she decided to mot speak anyway so I had to call back and was assisted by someone named Millicent who actually managed to assist me, so why is it that 2 people could assist and even go speak to their management and even check call recordings but the lady named Isa could not, what is wrong with her that she refused to do her job, she should not be working in customer service if that's the way her attitude is.