String or binary data would be truncated. The statement has been terminated

Hello,

After hosting service in IIS ; it shows me an error when trying to add a new record to a table .

Note: I read about this error and all the explanations were about the size.  I'm sure  with what I'm entering, that's not the problem.

what it shows exactly  is :

System.Data.SqlClient.SqlException (0x80131904): String or binary data would be truncated. The statement has been terminated. at System.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection, Action`1 wrapCloseInAction) at System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj, Boolean callerHasConnectionLock, Boolean asyncClose) at System.Data.SqlClient.TdsParser.TryRun(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj, Boolean& dataReady) at System.Data.SqlClient.SqlCommand.RunExecuteNonQueryTds(String methodName, Boolean async, Int32 timeout, Boolean asyncWrite) at System.Data.SqlClient.SqlCommand.InternalExecuteNonQuery(TaskCompletionSource`1 completion, String methodName, Boolean sendToPipe, Int32 timeout, Boolean& usedCache, Boolean asyncWrite, Boolean inRetry) at System.Data.SqlClient.SqlCommand.ExecuteNonQuery() at server.WebService.AddUser(String name, String phone, String email, String password) in C:\Users\user\Desktop\server\server\WebService.asmx.cs:line 139 ClientConnectionId:a365a08e-f7e3-491c-a378-1fa1f505d723 Error Number:8152,State:4,Class:16