I know this is a very late reply, but I find it essential for others to know. Honestly, the speed of your current plan (which is 2 mbps) is good enough to conduct inbound/outbound calls, provided that no other devices/PCs are plugged using the same source. But since we all have this data capping, you may find it difficult in the long run as you won't have a concrete idea to how many calls you will conduct and receive each day. Based on my experience, I would consume around 3-4G data every day - but this depends on the quantity and the intervals of each calls (let alone the length of time per call). My two cents, get a better plan or DATA Allowance, if you plan to have a steady connection especially when using VOIP. Trust me, you'll never regret at the end.