Question: what are data only sims?
Answer: A data-only SIM is self-explanatory. It's a SIM card that only gives you a data allowance and nothing else. ... Data only SIMs use the mobile data network of the operator you buy your SIM card from. So if you buy a preloaded data SIM from EE, you'll be using EE's 3G or 4G network to access the internet.