City Cab Company, LLC

We have been calling City Cab Co for quite a while but the rates always seem different even if our destination is always the same from south church street to [redacted] drive. There was one time the fare was only $10, then another time $13 then yesterday it was $16 and by the time we went back (from [redacted] Drive to [redacted] Street) it was still $16 and I paid through debit card, the driver gave me the receipt which is really $16 but when I checked my online bank account city cab co charged $18.40. The rates are inconsistent.