Welcome to Vodafone Community
Hi there im currently on the 50GB Red plan which was 36 a month , im getting a 15 pounds per month discount so am paying 21 a month all in , if i upgrade to say red100 which is 37 a month will i still keep the discounts or will i have to cough up 37 a month ?
Unless you mean Vodafone Advantage discount where the employee discount would need to be renewed when the contract was changed in anyway.
The best place to check how long your discount is valid would be your phone application. Generally, the discount would be with the tariff you are on, when you upgrade this would be something to discuss with the advisor.
Also, look at third party deals, you can save month that way and move your number to the third party contract. If you use the search facility of the forum you can see how this can be done.