You can slowly move from this to cloud telephony sector offering SMBs sms feature. Competitive price and easy user interface along with analytics on ROI should provide an edge.
I think, i didn't provide much information in the question. We have a website where user subscribe with their Mobile No. and Indian Railway PNR. We send them their PNR status updates via bulk SMS package which we have bought from some third party service. Now each SMS cost us money, but we didn't figure out how we can make money by sending SMS to thouse users. (i.e. putting advertisement in SMS, but didn't find any Ad network provide such feature for SMS).