Your Tariff. Being accepted for month SIM only deal can indeed improve your credit rating.
Charges outside of allowance. Whether your phone is locked to your network depends on the network you're with and even on which handset you've got and which plan you bought it on. We've searched for and collated the most affordable SIM only plans the UK has to offer and put them in our price comparison above to make it nice and easy for you to narrow down your perfect plan.