Hi ​@gemmanorcott
 

Thank you for reaching out to us, please accept my apologies for any inconvenience caused in relation to the bill issues received.
When you change the bill date you do get charged for a longer duration dependent on the date chosen.
This is then charged from the date that the bill period is currently until the new date which is more than 30 days and this is why it is increased.

Please be advised that this is a once off bill and the bill will change back to your monthly line rental when the next bill is generated.

Thanks,
Hosai