What is the reason for "Invalid Mobile Phone" Error on the checkout form?
1. This could be rejected by DataTools.
Please either remove Phone validation from the Merchant Facility - data validation options.
Or, contact DataTools support and ask them why this is being rejected.
2. If using EziDebit and If this looks fine at the DataTools side of things, then please check with EziDebit support. They often validate the phone number some degree, but that is normally length.
3. Check you do not have a validation rule in place if the above does not work.