Sampling question for telephone survey.
This isn't my field, but statistically speaking, you will possibly invalidate your study if you change the parameters mid stream. 

However, you can gather the extraneous data, since it is cheap to do so. But isolate it and use it only as a guide to future work and, perhaps, to give yourself confidence (not statistical confidence) in the outcomes. 

If this is dissertation work, then knowing what you could have done differently is worth exploring and maybe including. But let the experiment you designed be carried out faithfully. Otherwise, at best, you will just confuse yourself with the results.