Returning of goods wrongly purchaesd

I have a Toyota Corolla 2003 model with a factory fitted radio in it. This radio does not have the functionality to play mp3 nor the use of a usb. I thought to buy a radio that has this functionality in it. I got a radio online at Online Bargains, paid and 4 days later got the package. Upon installation I realized that if I install this radio that I will lose all the functionality of the Toyota radio, like km/l, temperature etc..<br> <br> I am trying to return this and get my money back but no answer for the past 2 days.