Whether the immigration visa is Valid or Expired it cannot be changed to another visa type in the Philippines unless downgrade your current visa to Tourist Visa (9a).
Visa holders must go through the procedure of downgrading of their Immigration visas prior to the expiration date to avoid immigration problems in the future.
A foreign national must apply for the reversion of his/her immigration visa to Visitor’s /Tourist Visa to continue his stay in the Philippines legally.
(from filing and submission of complete documents)