Price discrepancies/Overcharged

Lastnight I made an online purchase - the delivery indicated free however charged for @checkout.This is not the first time Im Experiencing price discrepancies and been overcharged by Woolworths and they never refund my money. My last complaint was wrt price discrepancy, screenshots were emailed to Woolworths and they advised they escalated to their technical team and I never heard from them again. I want this to be sorted and be refunded all the overcharged amounts that you owe me, this is such inconvenience and I'm starting to loose my faith in you.