Roaming data pass billing schedule

[Kalah]

I'm a bit confused when it comes to the billing schedule for the Roaming Data Pass / Roam Abroad Pass

It's listed online as £ 15.00 / month recurring so when does this charge occur?
When does the allowance start & end? 
Am I billed at the start of the month or on my actual contract billing date? On my 'data and usage' page it also mentions under data allowance restart that it isn't applicable to the roaming data pass 

[XRaySpeX · Accepted solution]

It is charged on your billing date for that billing period.

The Roam Abroad Pass costs £15 per billing month from the billing month you order it (text ROAMING PASS to 150) until the billing month you cancel it (text STOP ROAMING PASS to 150). For all billing months during which you have the Pass it is charged at the full £15 (soon to become £25 on 18th Oct.). However if the Pass is carried over from the 1st billing month to the next it will be charged pro-rata for that 1st month alone.