There is a good blog SAP Cloud for Customer Phone Number Parsing and Formatting which gives a detail explanation about the parse logic of phone number parse logic in C4C. By default it allows the Alphanumeric Value to be entered, the reason of this behavior is explained in note 2525818 – In an Account and Contact, the Phone Number Allows Alphanumeric Value.

However, at least in China, a valid mobile phone number only consists of pure numeric values. The requirement of local customer is whenever the value other than pure number is maintained, the error message will be popped up and the save is terminated.

The fulfilled scenario is: for example if I input an “A” character in Mobile field and press save button, error message is raised:Here below is how to achieve this custom validation logic in Cloud Application Studio.

Create an extension field phoneInvalidRel in BO BusinessPartnerRelationship, and declare the error message to be raised when invalid digit is detected.Implement BeforeSave event. This event is responsible to check whether the mobile phone number consists of pure numeric value and set the check result into extension field phoneInvalidRel, which will be used by onSave Validation later.Implement OnSave validation, and simply use the check result stored in extension field phoneInvalidRel.In the runtime, when I enter “A” in mobile phone field and save, first the BeforeSave event is triggered,And then the onSave Validation is called.The above implementation could only cover the scenario that end user directly changes the mobile phone number which is technically modelled in BO BusinessPartnerRelationship. There is another possibility that end user will also changes the field on Root node of BO BusinessPartner, as a result the same logic should be done again on BO BusinessPartner as well.BeforeSave implementation on BusinessPartner Root node:OnSave Validation on BusinessPartner Root node: