TERRIBLE SERVICE!

I have had a Mobile Phone contract with them for almost a year, they have a tendency of Locking the device when they have not got their payment! My debit order Date is the 26th and they run they're on the 25th, I have told them many times to change and they confirmed they have still today my Device is Locked! I have sent emails all day since their Phone number NEVER works and 5 hours still no response from them, very terrible experience...