Something

private void Button1_Click(object sender, EventArgs e)
{
    int servicecharge = 10;
    int transaction = Conversions.ToInteger(this.TextBox1.Text);
    if (this.RadioButton1.Checked)
    {
        this.Label3.Text = this.Label3.Text + this.TextBox1.Text;
    }
    if (this.RadioButton2.Checked)
    {
        if (Operators.CompareString(this.Label3.Text, this.TextBox1.Text, false) > 0)
        {
            this.Label3.Text = Conversions.ToString((double) (Conversions.ToDouble(this.Label3.Text) - Conversions.ToDouble(this.TextBox1.Text)));
        }
        else if (Operators.CompareString(this.TextBox1.Text, this.Label3.Text, false) > 0)
        {
            MessageBox.Show("Insufficient Funds");
            this.Label3.Text = Conversions.ToString((double) (Conversions.ToDouble(this.Label3.Text) - servicecharge));
        }
    }
    if (this.RadioButton3.Checked)
    {
        this.Label3.Text = Conversions.ToString((double) (Conversions.ToDouble(this.Label3.Text) - servicecharge));
    }
}