In addition to my previous solution this solution based on Shristi Comments
Hey,
Shristi I've created a table
create table address(name varchar(25),pno bigint)
you can see I've used pno[PhoneNo] as bigint datatype
and saved data by using below code it works better and saving data successfully
SqlConnection con = new SqlConnection("Database Connection String");
con.Open();
SqlCommand cmd = new SqlCommand("insert into address values(@name,@pno)", con);
cmd.Parameters.Add(new SqlParameter("@name",SqlDbType.VarChar,25));
cmd.Parameters["@name"].Value = textBox1.Text;
cmd.Parameters.Add(new SqlParameter("@pno",SqlDbType.BigInt));
cmd.Parameters["@pno"].Value = Convert.ToInt64(textBox2.Text);
cmd.ExecuteNonQuery();