Need help! anyone good with messaging?

hey I have got a Nokia N70 and it is a internet/email phone. When i bought it i got told i could email to other peoples phones and they will get it just like text messages as i get GB allowance. Would love to know how I do this as i have to pay to get texts every month as they do ot come within my contract and I have all this GB of bandwidth that I do not use and could use on sendng emails/texts. Hope someone can help. Would be very happy thanks Stephen