This API call is for merchant accounts that are specifically configured for international processing.

{
  "Intl_VoidCredtResult": {
    "CreditAmt": 5.0,
    "ErrCode": 0,
    "ErrMsg": "",
    "FunctionOk": true,
    "RespMsg": "Succesfull VOID\/Credit",
    "TransID": "a88ed0e4-5a3b-11ef-b49b-46647bd59a7a",
    "TxApproved": true
  }
}

using System.Text.Json;
using SampleCode.Models;
using System.Net;
using System.Text;

namespace SampleCode.Services {
  public class DataRepository {
 
   public async Task<IntlVoidCreditResult> Credit(HttpClient client) {

      // the IntlVoidCreditResult object matches the data in the sample response tab
      IntlVoidCreditResult creditResult = new IntlVoidCreditResult();

      var request = new HttpRequestMessage(HttpMethod.Post, "https://easypay5.com/APIcardProcREST/v1.0.0/Intl/VoidCredit");
      request.Headers.Add("SessKey", "48872E0041F24449B93033303031413033393XX");      

      var content = new StringContent("{ \"TransID\": \"c4aff768-75dd-11ef-b429-3ec35e8ff979\", \"CreditAmt\": 1.00}", null, "application/json");
      request.Content = content;
      try {
        var response = await client.SendAsync(request);

        if (response.StatusCode == HttpStatusCode.OK) {
          var responseJson = await response.Content.ReadAsStringAsync();
          var root = JsonSerializer.Deserialize<CreditResult>(responseJson);
          creditResult = root.Intl_VoidCredtResult;

          // important values to check
          if (creditResult.FunctionOk != true) {
            string errMsg = creditResult.ErrMsg;
            int errorCode = creditResult.ErrCode;
            string addlInfo = creditResult.RespMsg;
            // log error condition to your system
          }
        }
        return creditResult;
      } catch (Exception ex) {
        // log any errors
        creditResult.ErrMsg = ex.Message;
        creditResult.FunctionOk = false;
        return creditResult;
      }
    }
 }
}