I am receiving harassing text messages.
...and if I can block this one person or if I need to change my number who do I call if I have a solo prepaid phone. or do I need to change my phone number?
Besides calling Solo Mobile to have the number blocked, I suggest you also contact the authorities to have this person harassing you reported. You can also have your phone number changed if you want. There are also phones that have black list features or you can download third party apps that will provide your phone with the feature. Once a number has been blacklisted, all calls from that number will automatically be rejected. Messages in the other hand will be moved automatically to another folder or be deleted.