diff --git a/SteamAuth/AuthenticatorLinker.cs b/SteamAuth/AuthenticatorLinker.cs
index a30c6a00e..39f1d99a9 100644
--- a/SteamAuth/AuthenticatorLinker.cs
+++ b/SteamAuth/AuthenticatorLinker.cs
@@ -150,7 +150,12 @@ namespace SteamAuth
 
         private bool _addPhoneNumber()
         {
-            string response = SteamWeb.Request(APIEndpoints.COMMUNITY_BASE + "/steamguard/phoneajax?op=add_phone_number&arg=" + WebUtility.UrlEncode(PhoneNumber), "GET", null, _cookies);
+            var postData = new NameValueCollection();
+            postData.Add("op", "add_phone_number");
+            postData.Add("arg", PhoneNumber);
+            postData.Add("sessionid", _session.SessionID);
+
+            string response = SteamWeb.Request(APIEndpoints.COMMUNITY_BASE + "/steamguard/phoneajax", "POST", postData, _cookies);
             if (response == null) return false;
 
             var addPhoneNumberResponse = JsonConvert.DeserializeObject<AddPhoneResponse>(response);
@@ -162,7 +167,9 @@ namespace SteamAuth
             var postData = new NameValueCollection();
             postData.Add("op", "has_phone");
             postData.Add("arg", "null");
-            string response = SteamWeb.MobileLoginRequest(APIEndpoints.COMMUNITY_BASE + "/steamguard/phoneajax", "GET", postData, _cookies);
+            postData.Add("sessionid", _session.SessionID);
+
+            string response = SteamWeb.Request(APIEndpoints.COMMUNITY_BASE + "/steamguard/phoneajax", "POST", postData, _cookies);
             if (response == null) return false;
 
             var hasPhoneResponse = JsonConvert.DeserializeObject<HasPhoneResponse>(response);
diff --git a/SteamAuth/SessionData.cs b/SteamAuth/SessionData.cs
index 40905b92e..692ae60a9 100644
--- a/SteamAuth/SessionData.cs
+++ b/SteamAuth/SessionData.cs
@@ -34,6 +34,7 @@ namespace SteamAuth
             });
             cookies.Add(new Cookie("Steam_Language", "english", "/", ".steamcommunity.com"));
             cookies.Add(new Cookie("dob", "", "/", ".steamcommunity.com"));
+            cookies.Add(new Cookie("sessionid", this.SessionID, "/", ".steamcommunity.com"));
         }
     }
 }
diff --git a/SteamAuth/SteamGuardAccount.cs b/SteamAuth/SteamGuardAccount.cs
index 054b95e22..1da6ae69f 100644
--- a/SteamAuth/SteamGuardAccount.cs
+++ b/SteamAuth/SteamGuardAccount.cs
@@ -217,7 +217,7 @@ namespace SteamAuth
         {
             string url = APIEndpoints.COMMUNITY_BASE + "/mobileconf/ajaxop";
             string queryString = "?op=" + op + "&";
-            queryString += _generateConfirmationQueryParams(op);
+            queryString += GenerateConfirmationQueryParams(op);
             queryString += "&cid=" + conf.ConfirmationID + "&ck=" + conf.ConfirmationKey;
             url += queryString;
 
@@ -235,11 +235,11 @@ namespace SteamAuth
         public string GenerateConfirmationURL(string tag = "conf")
         {
             string endpoint = APIEndpoints.COMMUNITY_BASE + "/mobileconf/conf?";
-            string queryString = _generateConfirmationQueryParams(tag);
+            string queryString = GenerateConfirmationQueryParams(tag);
             return endpoint + queryString;
         }
 
-        private string _generateConfirmationQueryParams(string tag)
+        public string GenerateConfirmationQueryParams(string tag)
         {
             long time = TimeAligner.GetSteamTime();
             return "p=" + this.DeviceID + "&a=" + this.Session.SteamID.ToString() + "&k=" + _generateConfirmationHashForTime(time, tag) + "&t=" + time + "&m=android&tag=" + tag;