If you have a broadband connection we at Vonage can help you make calls to Portugal from the UK very cheaply, Gabriel. For just £7.99 a month you can make unlimited landline calls within the UK and to 14 other countries including Portugal. Check out our V-Plan 2 service at http://www.vonage.co.uk/call-plans/vplan2/
We are offering a 30 day money back guarantee so by all means give us a try.