Nope! You can't use Dr. prefix infront of your name after completion of the M.Phil. If you practice after M.Phil then you will be addressed informally as Doctor by your patients but if you want to use the prefix in front of your name, then you have to mandatorily complete the PhD.

To know more about Clinical Psychology, visit the link below:

https://www.careers360.com/courses/clinical-psychology-course

I hope this answer helps. All the very best for your future endeavors!