Apart from exceptional circumstances, we would not expect a customer to contact their water company by using another number (for example, by phoning an individual staff member on a direct line).
Ar wahân i amgylchiadau eithriadol, ni fyddem yn disgwyl i gwsmer gysylltu â'i gwmni dŵr drwy ddefnyddio rhif arall (er enghraifft, drwy ffonio aelod penodol o’r staff ar linell uniongyrchol).