Its normal in the signing world to cancel appointments, perhaps 20% of the time. Conditions change, and feelings change. However, if a company cancels more than 25% of the time, then perhaps they are not responsible in one or more facets! In such a case, either stop working with that company unless they will pay you for your travel time. Or, put them "at the bottom of your list". This means, only work for them when business is slow. Don't work for such an unreliable company at the end of the month when business is brisk.