Yes, if you keep going over your allowance then it’s probably a good idea.
You can move up to one of our other plans whenever you like without extending your contract. Just log in to www.btcom.ll-digital-sandbx1.bt.com/mymobile where you can also see what you've used and choose the best option.
Got too much data? No problem, you can easily move down a plan at www.btcom.ll-digital-sandbx1.bt.com/mymobile.