The Phoenicians were not anywhere near the Thermopylae Pass, so they could not betray the Greek force there.
The Phocians did not betray the Greeks at Thermopylai. They were given the job of protecting the track to the west of the pass, and when 10,000 Persian infantry came along the track to outflank the pass, the 1,000 Phocians were unable to block them.
Thermopylae
The pass of Thermopylae.
Thermopylae, as part of a force of 7,000 Greeks blocking the pass.
The Pass of Thermopylae.
The Greeks defended, the Persians attacked to get through the pass into southern Greece.
The narrow coastal pass of Thermopylae . August or September 480 BC
Its blocking of the pass was designed to precipitate a sea battle to defeat the Persian navy. Unfortunately for the Greeks their fleet lost, and the force at the pass was withdrawn.
Holding the pass at Thermopylae was used to force a naval battle. The Greeks lost the naval battle, so it was to no avail or effect.
At Thermopylai there was a pass to defend, at Salamis there was a narrow strait. Both negated the superiority of the Persian forces.
It was a delaying position holding the pass. When they were withdrawn, the Spartan and Thespian contingents remained behind to let the others get away. It was a noble sacrifice.
The Greek force at Thermopylai was not defeated, it was withdrawn. The Spartan and Thespian contingents remained holding the pass to let the other contingents get away and were anihilated.