Optus iPad Pro mobile data loss

Out of nowhere my IPad Pro 5 lost all mobile data information & now won’t connect. It was with Optus but suddenly lost all information on Optus out of the mobile data section & replaced with the only options being GigSky RedteaGO & Truphone. Optus are looking into it but have no idea & said everything is fine on their end. I’ve seen a few other people online have them same issue but no one has advised how to fix. Help please