why have i received a random text saying my apple id has been locked?

Are you sure the message is legitimate? Does it contain a link for you to sign in somewhere? It may be a scam.

Apple will always address you by your name or the name they have on file for you, not Dear Customer, Dear Client or by using your e-mail address. The e-mail will be from @apple.com or @iTunes.com. E-mail addresses can be spoofed. You can go to Mail/View/Message/Show all Headers to see more. Apple e-mails will never contain an attachment. Apple will never request personal information such as Social Security numbers. Apple won't send you a text telling you your ID is locked.

Avoid phishing emails, fake ‘virus‘ alerts, phony support calls, and other scams

Identifying legitimate emails from the iTunes Store