Incorrect sizing of shape wear

The sizing of your shape wear is incorrect. I bought a large, extra firm support (whatever you call it) 2 weeks back at your Cape Gate branch. I took the large according to the siz specs and my body measurements. It's not firm at all and provides very minimal support. I bought it so I can wear it while weight training at the gym. But it was a waste of money. There is minimal control and minimum support. It should support and compress the bottom tummy area, the mommy pouch, but this underwear does not do that. Whoever is buying these in should check it before signing and confirming the order. I went back, this time I wanted to fit on the medium and the small, before buying but the lady said Woolies does not allow this. What happens to my money I spent on the large. How do I get the correct size? The measurements and sizing on the ones in store are incorrect and measured wrong.