Though Smarty operates on Three's networks, the offer outdoes Three's current "6 months half price" unlimited data SIM-only deal. Three charges £22 per month for that plan, but has a reduced rate of £11 for the first 6 months of the 24-month term.

Smarty's plan is the obvious choice if you don't want to be tied into a contract for two years, but is it the best unlimited data deal out there? 

Smarty's offer is undoubtedly good, but is more expensive if you are deciding on a long term provider, in which case, Three's offer saves you more over a 24-month period  (compared to staying with Smarty for two years).

With Three the total cost comes to £462 over 24 months (£11 x first 6 months + £22 x 18 remaining months), whereas Smarty's rate totals to £480 (£18 x first 12 months + £22 x 12 months). You effectively pay £18 more with Smarty.

There's also the added benefit of 5G connectivity with Three as well as uncapped speeds, whereas Smarty's plan only offers 3G and 4G connectivity.

The verdict? If you prefer a short-term saving and the freedom to change providers after a year, go for Smarty's unlimited SIM-O deal for £18 per month.

If you want to save long term with have 5G connectivity, opt for Three's unlimited data SIM for £11 the first six months.

We're separately comparing all unlimited data deals in the UK if you want to see what the rates are from providers like Vodafone and O2.