Why is my Huawei CUN-L02 asking for a SIM network unlock PIN?

[punylittlehumanoid]

During a recent trip overseas my phone has lost all SIM functionality and keeps prompting me for this, seemingly at random (not just whenever I try to use SMS). I haven't tried to change carriers and the SIM card is undamaged and correctly inserted. I can't find information on this from my carrier's website, spark.co.nz, and all results on Google seem to address changing carriers. Would love some light shed on this.

 

[rgd1101]

contact your carrier

 

[punylittlehumanoid]

I took the phone in to an outlet of theirs to get it checked out; they gave me a spare SIM card to try with it and the phone worked fine.

I had been using the SIM card for years but had cut it down 13 months earlier to fit my current phone. Turns out it just died really, really slowly.