Nginx proxy remove spesific path and emty Post request body

I'm using nginx for web service proxy. I have rest service as below and i want to proxy my domain with suburi

https://www.example.com/myRestservice

Service has some method like this;

http://1.1.1.1:123/api/work/method1
http://1.1.1.1:123/api/work/method2

As result i want to access to methods of service like

https://www.example.com/Restservice/api/work/method1..

When i try to use rewrite in nginx as below, i can access service. But in this time Post method's request body is emty. I can see service logs.

In my nginx.config

upstream RestService {
   server 1.1.1.1:123;
   server 1.1.1.2:123;
}
server {
       listen                443 ssl;
       server name           https://www.example.com;

location ~ ^/Restservice/ {
          
   add_header Access-Control-Allow-Origin *;
   rewrite ^/Restservice/(.*) /$1 break;
   proxy_pass http://Restservice/;
   proxy_http_version  1.1;
}
}

I try to location part like this, result is same.

 location   /Restservice { 
   
   proxy_pass http://Restservice/;
}

In nginx access log;

status : 500 request: POST /Restservice/api/work/method1 HTTP/1.1