If you are going to send SMS in bulk to promote your shop please be careful of what time you are sending it. One of my clients yesterday sent a few hundred SMSs to his clients advertising a sale for some products for Wimbledon tennis.
The SMSs went out at 2:00am. Although we do not think that any law was broken, I doubt many of their clients would be pleased with getting SMSs at that time. If you are using SMS, which under our group deal is now even more economical, please send them, it at a reasonable time, you may find this useful as a guide on this question.