SIM-only deals on the Three network

Short answer: the cheapest is Smarty 5GB at £6.00 a month true cost (£72.00 over 12 months).

Cheapest: Smarty £6.00/mo true cost8 dealsMedian £/GB: £0.25 (all deals we check: £0.24)
NetworkDataContractTrue monthly cost£/GBAction
Smarty
on Three		5GB30-day£6.00
£72.00 total		£1.20Get dealAd
Smarty
on Three		16GB30-day£8.00
£96.00 total		£0.50Get dealAd
Smarty
on Three		20GB30-day£9.00
£108.00 total		£0.45Get dealAd
Smarty
on Three		40GB30-day£10.00
£120.00 total		£0.25Get dealAd
Smarty
on Three		100GB30-day£12.00
£144.00 total		£0.12Get dealAd
Smarty
on Three		150GB30-day£15.00
£180.00 total		£0.10Get dealAd
Smarty
on Three		200GB30-day£17.00
£204.00 total		£0.09Get dealAd
Smarty
on Three		Unlimited30-day£20.00
£240.00 total		—Get dealAd
Prices checked “Cheapest” = lowest true monthly cost of the 8 deals shown. Methodology

True monthly cost includes intro prices ending and any April price rises, shown in £/p as Ofcom requires. How we calculate true cost

Black Friday news: iD Mobile's half-price SIMs and what they really cost (checked 11 November 2026, no April rises).

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