Very Poor Service

I bought a king koil medium comfort bed on 03 July at Springfield and after making the payment I realized the invoice was written Firm comfort of which I asked the sales guy about and he informed me that it's what all the invoices say but assured me I would be getting the bed I wanted, the bed arrived a few days later only to find that it was the firm comfort instead of the medium comfort I had ordered. I then called the shop and spoke to the sales guy who assured me it was medium comfort the bed only felt firm because it was still new, he then told me that it would take roughly 30 days for me to get used to the bed. I went to the store on the 25th of September to ask for the comfort exchange because I was still not happy with the bed the lady who helped me told me that the guy who sold the bed to me was out and would be back in about an hour so I decided to wait and while waiting the lady decided to help me look for another bed but when she looked at the invoice she also questioned the description because I had shown her the bed that I initially wanted to buy and she told me that it was not what was written on the invoice, she then told me that in order to get the bed I had wanted initially I would have to pay R1 300. I ended up leaving without being assisted because the guy who had helped me still wasn't back after waiting for 1:30min. Why am I expected to pay for the mistake the sales guy made, would've thought they would call me but I haven't heard from them since. I am very disappointed as I had left a very good review on Google but now I'm gonna have to change it.