I have a monthly voice/data plan, and I have already surpassed my data limit with a couple of weeks to go in my billing cycle. Is there a way I can add on another 1GB for the month and pay a flat rate? I've already received a message saying that I have incurred an additional $10 in data charges. I thought it might be cheaper to top up (or add on?) another 1GB for this billing period. Thoughts?