You have some possibilities. First if you have to identify that is a invalid contact number. base on it you have to change the process flow. Second if you get error in find element may be you can set true in the “ContinueOnError” property or Element Exists activity. Third you can use the try catch. But I don’t know why are saying that do not use the try catch activity.Below i have attached the help link also.
Oh, the reason I’m not using TryCatch is the flow error message shown is not a main flow.
Using FindElement or ElementExists in TryCatch’s Try part, it take time everytime when error message is NOT shown. Am I making sense?