There should not be any discrimination against prepaid numbers... a number is a number and with today's technology the number is stored as a name so it should really matter.
I think, to be more precise, it's 09778xxxxxx. There are also prepaid numbers with 0977 prefix. I think it's even better if they dont put a specified prefix for postpaid. Prone kasi sila sa scams - lalo na yung share a load scheme.