how do I know if a text is a scam??

It is a scam. 100%

I don't even need to see the message to know that.

Think about it for a second. If you don't normally get notifications for every single transaction, why would you get one now?

Check for typos and grammatical errors in the text. Chances are there are several.. most common are things like 'iCloud id' where, a) ID should be capitalized, and b) it's now called an Apple Account, not an iCloud ID. It probably also quotes 'apple pay' or 'apple care' where Apple would NEVER forget to capitalize their own company name and service.

There isn't much you can do about it other than than remain alert.

Also you would never call a phone number or click a link in an email and provide any personal information. That single rule will prevent every such phishing attempt. You would always want to verify any information provided in an email/message using known contact information, not from something seen in an email/message. For banking information, you would know the means for you to contact them.

All phishing attempts will start with a message intended to scare you, followed by a means to resolve the problem with a phone number or link so they can get your personal/financial information.

Actually it is even easier than that. You simply NEVER call a number provided to you by an email/message. That works for any message you receive and does not require you to download any app or use a service.

I’m willing to bet that the text message was SMS and never mentioned you by name.

That’s all the evidence you need to block, report and delete the message.

If you receive a suspicious email or SMS text message that looks like it's supposed to be from Apple, please email it to reportphishing@apple.com. 

Learn how to ⇢ Recognize and avoid phishing messages, phony support calls, and other scams.

Good luck! 👋🏼😉

Perhaps a common scam message like the following:

Generally those SMS request you click a link or call a suspicous message.

You can consider some 3rd party app like Trend Micro ScamCheck to help you block those scam SMS and calls.

Please DO NOT click the suspicious link or call back the number in the SMS.

[Edited by Moderator]

Another easy method. Here’s what genuine texts from Apple look like.

Notice the check marks ✅ under the Apple logo in bottom image and next to name in top image.