Yes, for you to legally send ongoing, recurring SMS or MMS marketing messages to customers, you must have received prior written express consent. This process, called opting-in, allows customers to receive permission-based text marketing alerts.
Companies (the senders), are required to provide certain disclosures and instructions to consumers on how to opt-out of a marketing campaign. Make sure the marketing firm you engage with takes compliance seriously as there are rules, regulations, carrier requirements and industry best practices that must be complied with. Fines and penalties for sending spam or unsolicited messages can be quite significant.