"Free" to enter competitions

I have an old email address that I just use for those offers that are always cropping up. The amount of free to enter competitions that I get is ridiculous. TANSTAAFL. (Ther ain't no such thing as a free lunch.) When you get into these competitions you find that at some point they want your mobile number. If you supply your number you are then bombarded with texts that cost you money to answer questions. The text can cost a pound each so if you have a pay as you go mobile you can soon lose all your credit. Free? Bah!!!