unfair business practice

i did my eye glasses at Kelzmo eye wear in Maponya mall in January and paid R1200. Now in August i lost my glasses , i went back so i can get new glasses . The receptionist called the optometrist assistant , who then asked me to choose a frame , i did and told her i will put a deposit of R500 , she went inside of the optician room , came back with a receipt that's states my balance is R490. Saturday the 17th , they called me to inform me that my glasses are back and i need to pay R825 , not R490 as they have made a mistake , the prices have gone up . i asked them the receipt then was misleading and how then is it my problem that i was not told that the prices have gone up and how is it my mistake . they just said i must pay R825 that's it .

********* business practice