I assume by "chip" you mean the frequency crystal?
If your friend removed the frequency crystal for 153.235, installed a frequency crystal for 154.145, then tuned the pager for the new frequency (an important step which requires special equipment)...then the pager will operate on the new frequency.
As far as the tones, those are controlled by the Permacode active tone filters, and are completely separate from the frequency crystal. You would need to install the correct tone filters for your agency in order for the pager to alert correctly.