Unfair treatment

I went to Sleep Masters at Springs Avenue to look for as bed as and washing machine. Sibongile assisted me and we agreed on the items I choose but the installment was out of my budget but she had already processed the transaction (contract *** - R811.72). I later went back to Sibongile and explained my affordability doesn't allow me to pay so much for 36 months, we came to an agreement to remove the bed and only take the washing machine (contract reference *** - R474.40). All this was done on the 05/05/2025 and the Debi Check was sent was and I approved it. The washing machine was delivered on the 13/05/2025 but unfortunately it was not the one I choose and the total repayment amount changed from R8000 to R14000. I called Sibongile and she kept convincing me that I made the to right decision and I should keep it and they can't collect it because 7 days have passed for them to d look anything. Out of frustration from not being helped, I called the head office and was told to go back to the store since they are not able to do anything about them collecting the washing machine. I'm feel as a customer I'm not being heard and I'm being treated unfairly. Please assist with this matter urgently.