If your cellphone runs apps, look in your app market for Mr. Number (if you live in the US). It will block unwanted calls and SMS. I have it, it's free and works great. If you don't live in the US, look for an SMS blocker, and if your phone doesn't run apps, contact your service provider.
I would also advise you to check your phone bill-sometimes scammers use SMS messages to steal money from other people's accounts.

These people aren't calling me but they are texting me like crazy

If your cellphone runs apps, look in your app market for Mr. Number (if you live in the US). It will block unwanted calls and SMS. I have it, it's free and works great. If you don't live in the US, look for an SMS blocker, and if your phone doesn't run apps, contact your service provider. I would also advise you to check your phone bill-sometimes scammers use SMS messages to steal money from other people's accounts.