Sim contacts disappeared following forced switch

[EmmaLFC]

My forced switch from Virgin Mobile is taking place today. So far I have had 2 texts with log in details for Myo2 (a link that doesn't work) & a notification saying my operator had changed settings which was to switch on the emergency alerts. My phone now says o2 however I have some sim card contacts missing.

This forced switch could not have come at a worse time as my baby is having surgery on Friday so I need my phone to work, I have no other way of being contacted. Please can someone advise what has happened to my contacts! There was no mention of needing to back up contacts, only voicemails. I am very concerned that something else will go wrong.

[madasaf1sh]

@EmmaLFC 

The o2 switch on Virgin has nothing to do with loss of contacts, as you have been moved multiple times with Virgin Medai (EE, To Vodafone, to O2 to O2 MNO) 

If your contacts where on the SIM then it could actually be a faulty sim card rather than anything been done..

I would check if they are backed up to Google or iCloud (Phone depenedent)

For future reference you should always save phone numbers to the phone, and let them be backed up.

[EmmaLFC]

I moved from Plusnet to Virgin a couple of months ago & only because Plusnet was closing. That move was fine. The missing contacts were there yesterday - I text both. They were there this morning before my phone said o2, now they are not so one would naturally surmise that the switch over had something to do with it. I don't understand how my sim could suddenly become faulty.
My contacts are backed up. My question is what happened? Why was there no warning this could happen? And I also bring it up because I am worried about what else could go wrong when I have never needed my phone more than I will in the next few days.