Cell phone number change ***

I have 3 cell phone contracts and 1 data contract with Vodacom and been a client for many years. One of the contracts was for my mum (renewed in Dec 2016). My mum passed away in April this year. I requested that Vodacom please change the cell phone number ********** 391, i was told it cannot be done. What **** is that? I am not cancelling the contract just a change in cell phone number, surely Vodacom can understand the reason as to why i want the number changed. Deayon ********** 974