You can change your billing preference in Online Customer Service as you have to register in https://ocs.celcom.com.my or you can call 1-300-11-3282 for Celcom Home Fibre careline. Charges : RM0.30/Min : Operational Hours : 8.00am-12.00am.
Unfortunately, Celcom still doesn't send customer's bills to their email. BUT! You CAN get them from their Online Customer Service portal. To access, just go to their Celcom website and click at the "My Account" button at the to right corner.
As for payment, you can pay with maybank2u. No problem with that at all.
You can refer to their general FAQ for their Payment channel list if you want to know about other ways you can pay.
Hope this helps~