Thanks for your post - your post has been edited by a Mod, and skipped by the Help and Support Team. I want to get this sorted with you though, so I hope you will forgive the late reply.
We did have an issue that may have impacted your service in March - from 11 - 16th of March, the usage of a small number of customers was not collated in time to be added to your March bill. This issue was identified and resolved on the 11th of April, and some charges for your March billing cycle may have appeared on your April bill.
If these extra charges have resulted in you exceeding your cap for your April billing period, this is definitely something I want to resolve with you. We can't share your personal details here in the Community, and so I'd like you to email me through this information to email@example.com, using 245CKJBE as the subject field.
Using your unique code as the subject field means I'll receive and be able to action your email quickly and resolve the issues you've raised.