This is code to update customer phone number on AX2012 R2. You can check this code through simple small job.
DirPartyPhoneNoView PhoneNo;
ContactPerson contactperson;
CustTable custTable;
custTable = CustTable::Find("C45102");
PhoneNo = PhoneNo::find(custTable.Party);
PhoneNo.Locator = '6567767657';
PhoneNo.Type = LogisticsElectronicAddressMethodType::Phone;
PhoneNo.IsPrimary = true;
contactPersonEntity.createOrUpdatePhoneNo(PhoneNo);