Hi I am an agent for a truck rental co they are accusing me of using there trucks without renting them my contract says I am responsible for a dollar

A mile that I can't account for also they are accusing me of taking advantage of there fuel program ie stealing gas they are so posed to trip trucks off as needed instead they had me pick them up and the told me to lower the fuel level at ck in to compasate for my time and fuel also I had a lot of customers return trucks on empty and there credit card was declined