Last week I received an SMS from reliance regarding this.
As per government policy, from 1st Sep 2007, all SMS codes & Voice based services must start with “5” for all operators & vendors. So Please add 5 to all SMS codes & Voice based services .(Eg. 1234 changes to 51234). [link, link]
Have your mobile service provider informed you about this? Do you see this change has been made for your services?