Damaged goods sold/ health impaired

On 27/07/2014, I purchased an Electrolux Compact Vacuum Cleaner (*** S/N:01) from Hi-Fi Corporation N1 City. I had to pay somebody to take me. The box the vacuum cleaner came in, was broken & damaged & I asked the assistants for another, but they said it was the last one. I bought the vacuum cleaner for my mom, who needed something compact with great sucking power, due to her recent colostomy. My mom started using it the following week, but after 1 bedroom, she realised it did not suck. She packed it away & not wanting to sound ungrateful, said nothing. I noticed that the house was dusty & it affected my sinus & my mom's lungs. I unpacked the vacuum cleaner & noticed it looked old & had scratches on it. I then plugged it in but noticed it had no suctionand had to use broom & duster, which aggravated my sinus. My mom finally confessed that she did not use the vacuum cleaner because it was broken. Took it in for repairs on 11/10/2014 and fetched it after 23 days. They replaced the motor? I offered to pay the difference for a different machine, was refused. On 01/03/2015 back it went, same problem. I do not want the same vacuum back as it wastes my time & money. Please help.