Going through Tesco's mobile International Card is significantly cheaper than through other traditional means (rival calling cards, lebara, omni, lyca, talkmobile, orange camel, t-mobile international PAYG, vectone). You pay 4p connection fee per call and get a 0208 number which means that you can dial from any lines (mobile, BT, VM). For e.g. Calls to Mauritius are only 4p compared to 10p on others. Until the end of the month, you get £10 off a £20 card and you can top it up at any Tesco stores (you need to download and print a voucher). You will get clubcard points AND cashback (if you use a CC) and the funds last 90 days.