Virginmedia email calendar disappeared from Apple Calendar

Yesterday when i went to add an event to my iPhone Calendar app, all my previous events had disappeared apart from my outlook email calendar events.  I dug a little deeper to note that in the email calendars for the iPhone calendar app, Virgin media email account was no longer available to be selected.  It would only allow synced calendars from outlook or exchange email addresses.  I've tried to contact Virgin by chat but they are completely useless.  I've had a virgin email address for 20 years+ and its my main account, but if this is not a glitch, error with Apple calendar sync or a virgin problem that they know about and can resolve, i will slowly make the transition of all my accounts, logins, contacts away.  Its the one thing that has tied me to Virgin.  Can anyone help on the calendar thing? has it happened to anyone else?