Poor service delivery

I am a very irate customer. On the 17th July 2020, i did an online purchase. I was overbilled for one of the items. I sent an email on the 19th to advise of the overbilling. An agent called me on the 20th to acknowledge the email and confirm that i was overbilled. To date which is the 31st of July i jave not received my refund. I called the agents onky to be told they cannot find the refund on the system. Please can this matter be treated as a matter of urgency. If no refund is received in the next week, i am going to hold Woolworths liable for interest on the refund and they will be expected to pay me the interest together with the refund