Getting your money back it's so hard!!!.

On the 3rd of May 2019 I went out for lunch with my family to the burger king restaurant in Maponya Mall. Everything went well until payment time. I ordered three meals and onion rings on the side only to find out that onion rings where out of stock. I was therefore told by the manager that the money will be reversed back to into my account cause they could not give me cash, then they did the entire process of refunding me, only to find that the process did not go through. Then I made another payment thinking my money was refunded while it wasn't so it means I payed for one meal twice (double the amount of the meal was taken) . I reported the matter immediately that day but didn't get help, instead the assistance took my number and promised to come back to me but never did. I decided to go back to the restaurant to lay my complaint for the second time and they told me that I would receive my money after 7 to 14 days. 18 days have passed and still no response from the restaurant. May i please be helped. Thank you.