I'm so sorry things aren't working out as you had hopped. But this sounds like it's entirely about their poor planning / expectations & that it's not about you or your capabilities as a phlebotomist at all.

If you really like the phlebotomy part of the job and the people there, it might make sense to stay & look for something part time in the afternoons. That would also keep you current on your resume so that in a year you could look for a full time position?

If that doesn't feel like an option, how would you feel about doing lab work full time? Would it bore you or be challenging?