I need to work with stored procedures, with the help of Entity Framework Core. This is my function:

public async Task<bool> CheckIfUserRegistered(string phoneNumber, DateTime dateOfBirth)
    {
        if (string.IsNullOrWhiteSpace(phoneNumber))
        {
            return false;
        }
        using (var cmd = _dbContext.Database.GetDbConnection().CreateCommand())
        {
            cmd.CommandText = "dbo.CheckIfUserRegistered";
            cmd.CommandType = CommandType.StoredProcedure;

            cmd.Parameters.Add(new SqlParameter("@phoneNumber", SqlDbType.NVarChar) { Value = phoneNumber });
            cmd.Parameters.Add(new SqlParameter("@dateOfBirth", SqlDbType.Date) { Value = dateOfBirth });

            cmd.Parameters.Add(new SqlParameter("@registered", SqlDbType.Bit) { Direction = ParameterDirection.Output });

            if (cmd.Connection.State != ConnectionState.Open)
            {
                cmd.Connection.Open();
            }

            await cmd.ExecuteNonQueryAsync();

            return (bool)cmd.Parameters["@registered"].Value;
        }
    } 

I'm not sure, with the correctness of this function, is this the right way to work with stored procedures in EF Core? Don't I have problems with forgotten connections, memory leakings, etc?