I've been using Android for several years across multiple devices and versions; so I don't think I've missed anything obvious here; but you never know...

Just bought my wife a new Spark-badged Samsung J5 Pro, which is running on a Skinny Direct SIM. My thinking was that the Spark-model phone would work better on Skinny Direct than the 2Degrees-badged phone [due to those obscure settings you can't change with respect to how cellphones and towers handle fallback etc].

However, the phone seems to have the wrong voicemail platform number loaded in it; I wasn't aware that Skinny and Spark used different voicemail platforms.

No problem, thought I; I'll just change that. However, attempting to do so just produces an error message 'Failed to read data. Voicemail number change unsuccessful'.

I assume that for reasons involving being "helpful" [i.e. not helpful!]; the Spark ROM has locked the voicemail number.

Any ideas on how to fix this welcomed!

[And Happy New Year all!]