web service deep insert Business central cloud

hello everyone,

I am using cloud Business central. I am trying to post the Sales header and sales lines In one API request. this is below what have done so far

I created the web service from sales order page 42

second, I used the following request, with the “expand” parameter

post

https://api.businesscentral.dynamics.com/v2.0/0000000-c73-0000-b675-c3cf000eb000/Production/ODataV4/Company(’####’)/SalesOrder?$expand=SalesOrderSalesLines

the post request is going with our errors, but no lines are created. though

get request is working fine and retrieve header and lines,