One solution for this will be to create a Dial-peer with higher preference than the ephone DN and then apply a translation rule to manipulate the digits however the way you want. Hope this helps
For example
dial-peer voice 1002
voip destination-pattern 1019
.
.
.
preference 0 <<=====This dial peer has precedence and will match first.
ephone-dn 1
number 1019
preference 1 <<======Configure lower preference for prebuilt DN.