The GDPR requires affirmative consent for each specific use of your data. If the company had previously asked you "Please tick this box if you would like to receive marketing messages from us in the future", they don't need to ask for your consent again but they do need to offer an opt-out. If the opt-in was pre-ticked, vaguely worded or mandatory to submit the form, then that consent is no longer valid and they'll need to ask you to opt-in. If you didn't specifically opt-in but were getting marketing messages because you had done business with them, they need an opt-in to keep sending those messages.