Use this call to determine if the purchaser has a card on file. If you have created the consent (card on file) using a reference ID or PatientID then you can use the following Query to return an array of Consents ( Card On File Info ) for a particular patient with this PatientID:
F='213456')&&(H=1)&& (C>='01/21/2024') This will return consents with a particular PatientID which are still enabled and have not yet expired ( use todays date ).

You will want to present the user with the last 4 digits of each stored card so they can decide to choose a stored card or simply enter a new one. Easy Pay offers multiple ways of querying consent data. View the https://easypaysoftware.com/en/Querying Query Guide for more details.

{
  "ConsentAnnual_QueryResult": {
    "Consents": [
      {
        "AcctHolderFirstName": "JOHN",
        "AcctHolderID": 1,
        "AcctHolderLastName": "DOE",
        "AcctNo": "1111",
        "AuthTxID": 15,
        "CreatedBy": "John_Doe",
        "CreatedOn": "\/Date(1549967986773-0500)\/",
        "CustID": 15,
        "CustomerRefID": "A12345NO-99",
        "EndDate": "\/Date(1581483600000-0500)\/",
        "ID": 12,
        "IsEnabled": true,
        "LimitLifeTime": 1000000.0000,
        "LimitPerCharge": 1000000.0000,
        "MerchID": 1,
        "NumDays": 365,
        "RPGUID": "",
        "ServiceDescrip": "",
        "StartDate": "\/Date(1549947600000-0500)\/"
      },
      {
        "AcctHolderFirstName": "JOHN",
        "AcctHolderID": 1,
        "AcctHolderLastName": "DOE",
        "AcctNo": "1111",
        "AuthTxID": 14,
        "CreatedBy": "John_Doe",
        "CreatedOn": "\/Date(1549967948037-0500)\/",
        "CustID": 14,
        "CustomerRefID": "",
        "EndDate": "\/Date(1581483600000-0500)\/",
        "ID": 11,
        "IsEnabled": true,
        "LimitLifeTime": 1000000.0000,
        "LimitPerCharge": 10000.0000,
        "MerchID": 1,
        "NumDays": 365,
        "RPGUID": "",
        "ServiceDescrip": "",
        "StartDate": "\/Date(1549947600000-0500)\/"
      }
    ],
    "ErrCode": 0,
    "ErrMsg": "",
    "FunctionOk": true,
    "NumRecords": 2,
    "RespMsg": "Successfully Returned Consent Records : 2"
  }
}

using Microsoft.AspNetCore.Mvc.RazorPages;
using System.Text;
using System.Text.Json;
using System.Text.Json.Nodes;

namespace SampleCode.Pages {
  public class ConsentQuery1Model : PageModel {

    public string msg = String.Empty;

    public async Task OnGetAsync() {

      // return all consents for merchant 1 with a Reference ID = CustID1234. json = { "Query": "(A=1)&&(F='CustID1234')"}
      string query = "{\"Query\": \"(A=1)&&(F='CustID1234')\"}";

      var client = new HttpClient();
      client.BaseAddress = new Uri("https://easypay5.com/APIcardProcRESTstaging/v1.0.0/");
      var request = new HttpRequestMessage(HttpMethod.Post, "Query/ConsentAnnual");

      // use your session key obtained when you authenticated 
      request.Headers.Add("SessKey", "3481DDAA24E94C31AA303237343341303337353938");

      var content = new StringContent(query, Encoding.UTF8, "application/json");
      request.Content = content;

      try {
        var response = await client.SendAsync(request);

        if (response.IsSuccessStatusCode) {
          if (response.Content == null) {
            logError("Response content was null");
            return;
          }

          string responseContent = await response.Content.ReadAsStringAsync();
          var jsonDom = JsonSerializer.Deserialize<JsonObject>(responseContent)!;
          bool FunctionOk = (bool)jsonDom["ConsentAnnual_QueryResult"]["FunctionOk"];

          //Check for unexpected errors. If errors found Stop Processing and check ErrorCodes
          if (!FunctionOk) {
            msg = (string)jsonDom["ConsentAnnual_QueryResult"]["ErrCode"] + " " + (string)jsonDom["ConsentAnnual_QueryResult"]["ErrMsg"];
            logError(msg);
            return;
          }

          // this just displays results as a string.
          msg = "Number of records found: " + jsonDom["ConsentAnnual_QueryResult"]["NumRecords"].ToString();
          msg += jsonDom["ConsentAnnual_QueryResult"]["Consents"].ToString();
        } else {  // request was NOT successful. Check and log error codes.
          msg = response.StatusCode.ToString() + ": " + response.Content.ReadAsStringAsync();
          logError(msg);
        }
      } 
      catch (Exception ex) {
        logError(ex.Message);
        msg = ex.Message;
      }

    }

    private static void logError(string msg) {
      // implement your logging function here.
    }
  }

}