First generate port code, voda would call you within 2-3days of code generation. bargain with them for this offer if not satisfied visit nearest retailer ask him for 28GB offer in any first recharge available? almost all cos atleast in Delhi are giving away this offer.How did you go about it? Did you put in a port out request with previous operator or with airtel who guided you through the process? Since vodafone ain't providing me with a good voice/4g data plan, i too am going to port out.
Also keep checking for offer on ur existing no , I have seen them getting a lot better after code is generated.