WHY MUST I PAY FOR SOMETHING THAT IS FREE

I took out a contact 2 years ago (P10 plus with a second handset "free"). This contract is/was due to end in May 2020 but as we all know, vodacom allows us to upgrade a few months before. I had upgraded my contract in January and now i see the "free handset" i had gotten for i being charge with now. How can i be charged for something that IS FOR FREE. Vodacom you are *******...... I made contact with you last week and somebody said i would be contacted.

IM STILL WAITING FOR YOU ******* TO PHONE ME