Hello Rawrxd,
Welcome to the community!
As FidoNick noted, mobile providers generally only provide the OTA updates for the devices they offer. Any updates need to be initially provided by the manufacturers to the mobile providers. If the mobile provider does not offer a particular device, the manufacturers do not provide the update for them.
I understand Rogers has the update listed in their schedule. That's because Rogers, at one point, did carry that particular phone (see here).
Now, before you decide to up and switch providers, what do you mean by international version? That is, what is the version number of the phone you have? As far as I am aware, there are a number of variants for that model -- most of them could be considered international (see here). The update provided by Rogers (or possibly other Canadian providers) might not suit your particular version of the phone. It would be for the version sold by Rogers at the time. You would need to the the specific OS update for your phone version. You would need to contact Sony (possibly from Country where your phone was purchased) to inquire how you might obtain the update.
Hope this helps 
Cheers
