How to use phone’s microphone with earphones plugged in?

So, i have an iphone 11 which does not come with a headphone jack. While playing game i use my JBL earphones which do not have built in mic. So whenever i turn on the in game mic then automatically the phone’s speaker activates and the sound comes from them and when i turn it off then it switches back to earphones. So what i want is that i use my earphones (without the built-in mic) and simultaneously use the phone’s mic. What’s the solution? Apart from buying the earphones with built in mic.