Are attorney flat fee trial retainer fees refundable?

I paid my attorney a total of $7000 to represent me in a criminal matter. I initially paid $3000 for the initial retainer fee. I had to pay an additional $3000 when the court scheduled the case for trial per the engagement agreement. I paid an additional $1000 for witness subpoenas costs for trial preparation.The case was resolved before trial. However, my attorney said he never subpoenaed any witnesses as he changed the defense strategy. I felt my attroney had not spent the time to adequately prepare for trial. The agreement does not state anywhere that the fees are non-refundable. Can I request a partial refund on the trial flat fee retainer ($3000) becuase it did not go to trial and a full refund of the subpoena/witness costs as the attorney never served witnesses?