Got 18 units of Botox 2 1/2 weeks ago, a week later doctor add 12 more units for a total of 30. Why do I still have frown lines?

Deeper wrinkles need a combination approach of Botox with fillers, lasers and microneedling/prp. See an expert. Best, Dr. Emer

There is a varying range of doses. It can vary from 30-50 units. If you wanted no movement then the initial dose of 18 units was probably low. Another way to approach it is to keep doing treatments every 3 months and after 2-3 treatments usually i find the frown lines disappear and you are still able to retain movements. 
Best Wishes