Changing tariff: when is new tariff effective?

[sunmat]

A few years ago I had the 30GB tariff and could use my data without any problem when on business trips to the US; during the pandemic I downgraded my tariff to 20GB as I wasn't traveling and didn't need so much data.

I'm currently traveling again to the US and don't have any network: I realized I need to either switch back to a 30GB tariff, which has the O2 Travel Inclusive Zone, or add the "O2 Travel & Higher Data Limit in non-O2 Travel countries" bolt on.

I would like to do the former, but I am not sure whether the new tariff will be effective immediately or at the next billing cycle (in which case I'll still have to add the bolt on to enable roaming while in the US). I read conflicting information: somewhere it said the new tariff would be effective within 24h, and somewhere else it said it would be effective at the beginning of the next billing cycle, i.e. in about a week (1st of March). Which is it?

[MI5 · Accepted solution]

@sunmat 

If you upgrade your tariff it will change within 24 hours.

If you just change the tariff, it will be at the start of the next billing period.

[sunmat]

@MI5I'm not sure I understand the difference. I tried selecting the 30GB tariff and before confirming it says "If you confirm, your new tariff will start on 01 March 2023 and will cost £28.75 a month."... so this looks like a tariff change, not an "upgrade"? or did I miss something?

[MI5]

@sunmat 

If you are out of contract, ie you have completed your minimum term, you can upgrade (it's a different section in your MyO2). If not, you can only change your tariff.

[sunmat]

Thanks! Indeed I was out of contract and I had to upgrade to a new 12-month contract with 150GB for 25£ to get the Travel inclusive zone again. Once I did, roaming became available on my phone. It's unfortunate that the difference between "upgrading" and "changing tariff" isn't clearer on the website.

[MI5]

You're welcome @sunmat