Can others see the content of the message?

You're right. There is a software to replace the SIM card. Press the phone to monitor the phone number you want to monitor.

There is also a whole mobile phone, where you can set the number, location, phone monitoring and SMS interception ... (Send me a spam message) Their product website www.aaa6688.com.

You can go and have a look, but be careful of viruses!

I suspect that your mother accidentally received spam messages and used their products. ..

You can calm down and talk to your mother. If it really doesn't work, you can be vigilant, such as showing her a legal white paper on this behavior. If you are above 18, this behavior is illegal!

Your mother is really out of line. She may be worried about you, but it's wrong to invade privacy again!