Mobile phone firm o2 has increased their “two free SIM card” offer to up to four free SIM cards. Each SIM comes with up to 500 free UK texts every month, worth up to £50 a month. To receive their free 500 texts customers simply have to top-up their O2 mobiles by a minimum of £15 a month. Get your SIM cards at freesimo2.o2.co.uk. Limited period, while stocks last.