Credit and Debit are bad terms really. Credit effectively means Visa, MasterCard, Amex or one of the other various signature networks and debit means one of the local domestic networks (although some Canadian and UK debit cards support US debit networks as they are partnered with NYCE Debit).

This only really occurs in a few countries like AUS,NZ and the US.

In most other countries a debit card always runs as a debit card (Either over a major card network or a domestic network), this is usually because of two reasons, either the card only runs on one of the signature networks and merchant just pays less interchange or a fixed amount on debit but the card doesn't actually process any differently to a credit card (The UK for example). Or the countries debit cards run on a domestic only network and while they may support Visa,MC or Amex they will only process over these networks outside of their domestic market (Canada or France).