It’s a funny old system, this Smart/Cellcard/Metfone setup. Networks that are not welcoming of each other. Very reminiscent of the UK’s cellphone network back in the early days. I’m actually surprised it hasn’t been overhauled.

Some posters won’t be aware, except from having read history books, of mobile phones the size of bike or small car batteries, which as they developed, through miniaturisation resembled Walkie-Talkies out of WW2. SMS cost by the character- not all of those short cuts were because of lazy thumb bandits B4is much cheaper than before; shorthand for SMS in the same way that there is/was shorthand for telegrams.

The other half has Smart, Cellcard, and Metfone sims, because various family members have either one, but don’t own or know how to use a smart phone. Calling a Metfone sim from a Cellcard runs the credit down quicker. It’s getting better as grandkids grow up and help the elders operate their phones, and messenger takes over.

As for the person who registered the sim card that nobody knows. Don’t be overly surprised if the staff in the shop don’t actually know each other’s real/official names. The sim cards are likely registered using an ID card, but the same person has always been known as Bob or some other nickname/short names.

It initially annoyed me when I asked the other half what one of her nieces names might be, and I’d get a semi embarrassed look by reply. But then, I found myself trying to follow a conversation among the family and kept hearing the same name pop up. Blank looks for a while until the penny dropped- they were referring to my other half by a name I’d never heard.
In fact, there’s three such nicknames for the other half, that I know of. One used by her circle of Phnom Penh friends and myself everyday, one more that is almost exclusively used by her brother and his family in Kratie, and yet one more that has been used by her Grandmother and great-aunt since she was tiny. Very few people call her by her actual name.

Kigna and Reckoning, I know nothing about either of you, and I’ve only been flitting in and out of Cambodia since 2018, myself. New shit annoys me all the time. Old shit that should have stopped is a minor irritation.
Go with the flow. You’ll get overwhelmed by the absurdity before you get very far, and then you’ll encounter something that’s really worth getting bent out of shape over, and you’ll not have capacity left for an appropriate reaction, and you’ll not enjoy anything.