SOLID [S] - Wrong Method

solid-S-wrong-method.cs

public Payment ProcessPayment(Payment payment)
{
    var transaction = this.BankService.CreateTransaction(payment);

    payment.AddBankTransaction(transaction);

    var mail = new MailMessage();
    mail.From = new MailAddress(payment.Merchant.Email);
    mail.To.Add(payment.Customer.Email);
    mail.Subject = "Bla bla bla";
    mail.Body = "bla bla bla";
    SmtpClient smtp = new SmtpClient("smtp.gmail.com");
    smtp.Send(mail);
    // code code code

    using (var sqlConnection = new SqlConnection(this.DatabaseConfiguration.ConnectionString))
    {
        var query = "INSERT INTO Payments (...)";
        var result = sqlConnection.ExecuteReader(query, payment);
        // code code code
    }
    
    return payment;
}