Thanks for using the forums to get this issue with your mobile data looked into, I am sorry it's become quite slow over the recent weeks/months.
Enlli's advice is correct, we have started a migrating process and all customers will be on the new network by approximately the first quarter of next year.
Can I ask if you're still within contract please? If you are, there may be a Buyout Fee attached to your cancellation (monthly cost x how many months you have left) I just wanted to make you aware of this so you don't get a surprise when you call our mobile retentions team!
If you need more help or advice, please feel free to reply and I will be more than happy to help 🙂