Consumers who conclude contracts with companies often already give their consent via the company's general terms and conditions (GTC). For example, that they agree to be contacted for advertising purposes. At this point, the company usually already lists several communication channels through which it wants to be able to contact the consumer.
You can find out here whether and under what conditions such consent is effective.
Legal background
Pursuant to Section 7 I of the Unfair Competition Act (UWG), the permissibility of commercial actions depends on legally effective consent. This includes advertising in particular. The requirements for such consent are, in particular, that it be formulated specifically enough and that it be freely revocable. In addition, the consumer must give it in an informed and voluntary manner.
In principle, such consent can also be obtained by accepting the GTC.
In a corresponding ruling, the Federal Court of Justice (BGH) states that consent within the meaning of Section 7 of the German Unfair Competition Act [UWG] is "any expression of will [that] is given without coercion, for the specific case and in full knowledge of the facts, and by which the data subject accepts that personal data relating to him or her be processed. Moreover, it must be possible to give this in any appropriate manner, whereby the user's wish is expressed in a specific indication, made in an informed and free decision" (BGH judgment of 01.02.2018 - III ZR 196/17).
Consent for multiple advertising channels
It is now questionable whether a declaration of consent that refers to advertising via several advertising channels is specific enough. The relevant GTC clauses often contain formulations such as: "In the future, I would like to be personally informed and advised about new offers and services from the company by e-mail, telephone, SMS or MMS. I agree to the processing of my contract data for individual customer advice."
According to the BGH decision already cited, separate consent for each individual advertising channel is not mandatory. As long as the consent is given without pressure on the consumer and with knowledge of all factual circumstances and the consumer agrees to the processing of his personal data, it can be effective.
By explicitly listing the advertising channels, it is clear to the consumer what he or she is consenting to. The consent is therefore specific enough. If the clause were to include further general contractual provisions in addition to the information on contacting, this would probably be assessed differently
Consent can also be given by simply ticking the relevant clause ("opt-in").
The user of the GTC (the company) always has the freedom to formulate the legal declaration in the same way as a sample contract on its own, so that the consumer is only left with the decision whether to accept or reject the declaration.
Conclusion
An individual consent can, if it meets the general requirements for consent, also apply to advertising via several advertising channels. It is given for the specific case if it is clear which products or services of which companies it specifically covers. However, the clause may then no longer contain further general contractual provisions, as otherwise it is no longer specific enough.