Lies and accusions by AVIS ... shocked

I had to give my car in for repairs and I was assigned a rental vehicle by Avis, by my insurer. There were struggles in obtaining a vehicle however after many phone calls I was assigned a vehicle. It was storming and I did advise to bring the vehicle the day after however the vehicle was on its way. Due to the storm, I could not inspect the vehicle however advised there was no issues to note so I trusted the advisor. Yesterday I returned the vehicle after 2 weeks and am told later in the day, that a plug was put on the tire. I'm more than anything upset that I was given a vehicle with a plug on the tire having to drive my child to and from school. Now Avis accuses me of putting the plug on the tire. My response is of shock and advise that the vehicle has tracker there fore track the vehicles locations when I had possession and note where a plug was put on. I am told they would have seen it before giving me the vehicle so it gives me the impression I am being accused yet I knew nothing of the plug nor did I put one on the tire. This is utter lies and I am going to escalate to my insurer and to senior management of Avis.