Getting weird spam texts - how to stop them?

Since last night, I've been getting spammed with these annoying Mailer-Daemon text messages saying I couldn't send a message to my Yahoo account. I will sometimes text a link of something like a recipe I want to remember to that email.

They have been coming in a lot. 4 or 5 at a time. They even came at 1:00am and woke me up. They are coming to my text/phone number, not my email. I removed my cell phone number from my yahoo account and changed my yahoo password. Will this help?

I scanned my phone with AVG Antivirus (free version) and it didn't detect anything. My phone is normal otherwise.

How do I stop these super annoying messages? Should I delete my yahoo email?

Getting weird spam texts - how to stop them?
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