Frustrating Text and Email Spam

I was impressed initially by how accommodating, professional and respectful they are. I am annoyed by how they bombarded me with 3 test messages, 3 or more emails every month reminding me to make a payment, giving me their banking details and advising me to deposit proof of payment even though we made an arrangement for them to debit my account. They have been debiting my account for over 3 months now and always get the promised amount and yet I get generic emails whose content sounds relevant to people who deposit the money into their account. I sent an email voicing these concerns - but I never got a response. Instead I got another email telling me to deposit proof of payment. I asked whether or not I am being charged for these pointless texts and emails and they never responded to my email.