Hello,
I purchased the same make and model of phone when Public Mobile was on the old CDMA network. If your phone functioned on the old network before Telus purchased PM, it is incompatible with the new network. Plus, it has no capacity for a SIM card, which the new network requires of all phones.
Are you sure that you are not confusing the SD expansion slot as where you believe a SIM card should be?
I hope that this has helped.