If you are getting the [b]'wap_push_si' in your text messages and it keeps coming back each time you delete it and reboot the phone. The problem will be that you have [b]Google Messenger installed. Google released an update to Google Messenger back on Feb 22, 2016 with a software bug causing this problem.
Make sure you are in your stock text messenger app that came with your phone, delete the 'wap_push_si' message from your text message app, go to add and remove apps and uninstall Google Messenger. Reboot the phone and the problem message will not come back.