annoying sms

They've been sending me new accounts numbers that I don't know and reference numbers since last year .I've been receiving sms from this company claiming that my subscription was successful and I must call them. Its the 1st time I heard about them from those sms. How can I stop this company from sending me this sms & how can I subscribe to a company I don't even know? Where do they get our details? I'm not their member and I won't join them.