Multilingual support is the entry on this site's service list that changes the pay conversation, and it is the reason the aggregate figures above should be treated with particular caution. A number built from three postings cannot distinguish an English-language retail queue from a premium language role, and the gap between those two is where the money is.
The economics are straightforward. The Philippines has an enormous pool of professional English speakers and a much smaller pool of people who can handle Japanese, Korean, Mandarin, Spanish, German or French at business level. Scarcity sets the price, so language-qualified agents are recruited against a different benchmark entirely, and they tend to stay longer because their outside options are also better.
If you hold a second language, three things follow. Put the proficiency level on the first line of your application rather than in a skills list at the bottom, since screeners triage on it. Expect to be assessed in that language, often on the same day, so treat any interview as a live test. And negotiate on the language rate rather than on the general agent rate, because they are separate structures and applicants who do not know that routinely anchor themselves too low.
For how shift-related pay layers on top of any of these rates, our iBEX Alabang guide works through the night differential arithmetic in detail.