My food was off

I ordered a bacon avo & cheese burger at Wimpy Springsgate. I ate my chips and when I took a bite of my burger it didn't taste right. The avo tasted off so my mom tasted it and said it has alot of lemon juice in it but the whole burger didn't taste right so my friend also tasted the avo and said it's off and that I should not eat it. So I took the top of the bun with the avo off and when I smelled the cheese and patty on the rest of the bun it smelled off so I didn't it eat it. When we paid the bill we told them that we weren't going to pay for my food because it was off and we told the waiter that the food was off when he finally came to our table. When we paid the bill and said we weren't going to pay for my meal because it was off they said we have to pay for it and after a while of telling them we weren't going to pay for a meal that is off they didn't charge us for the meal but they weren't very friendly and didn't even say sorry that the food was off.