Siebel adding charset utf-16 to header HTTPContentType for EAI HTTP Transport

We're tring to call a service using EAI HTTP Transport business service, SendReceive method.

But we have an error because siebel applends charset=UTF-16 to Content-Type header. Is there a way to remove this?

Thanks

User-Agent: Mozilla/4.0
Accept: application/json
Connection: close
Content-Type: application/json;charset=UTF-16
Authorization: xxxxx

HTTP response Headers from Data Send request:
HTTP/1.1 400
X-Frame-Options: SAMEORIGIN
X-Content-Type-Options: nosniff
X-XSS-Protection: 1; mode=block
Authorization: Bearer ….
Accept: application/json
User-Agent: Mozilla/4.0
X-Forwarded-For: …..
cneonction: Close
Content-Type: application/json;charset=UTF-16
Content-Length: 882
Date: Wed, 26 Feb 2025 09:55:20 GMT
Connection: close