I'm a customer of a bank and presumably they can claim legitimate interest for the account and service updates they send. However I also received an email and letter about their referral program where they offer money to refer new customers. I never explicitly gave my consent for any marketing purposes.
If I am a customer and I have given my consent to be contacted for things like service availability and payment notifications, does this allow them to contact me for other reasons like this referral program?
The company also says that their email and letter is not marketing material as it is not something that everyone will receive and it contains a code unique to me. This doesn't make any sense to me as it's clearly targeted advertising.
If this is not allowed how can I make a complaint about their behaviour?