1st argument: not an iodata term Error For multilingual text

I am trying to send a string of text as a body like this:

HTTPoison.post(
      "https://api.letter.net",
      '{"text": "{🇺🇸 : Hello #{message} welcome here #{number} \n 🇯🇵 : #{number} ようこそいらっしゃいました #{message} ハローウェルカム\n 🇰🇷 : #{message} 안녕 #{number} 여기 오신 것을 환영합니다}"}',
      [{"Content-Type", "application/json"}]
    )

But I am getting this error

[error] GenServer #PID<0.780.0> terminating
** (ArgumentError) errors were found at the given arguments:

  * 1st argument: not an iodata term

    :erlang.iolist_to_binary([123, 34, 116, 101, 120, 116, 34, 58, 32, 34, 127482, 127480, 32, 58, 32, 65, 32, 110, 101, 119, 32, 114, 101, 108, 101, 97, 115, 101, 32, 110, 111, 116, 101, 115, 32, 102, 111, 114, 32, 118, 51, 46, 49, 50, 46, 48, 32, 114, 101, 108, ...])

I know that this is because of the Japanese and Korean text but I am I did not find resources on how to send something like this…