Thanks for getting back to us @Cavallino.
Depending on compatibility, it's entirely possible for existing discounts to be required to be removed, when adding new services or upgrading/downgrading services. But also, even if the discounts are compatible, they would expire on their original expiry date and not renew for an additional 18 months from when you make new changes. For a clarity point of view, it would probably be best to make your changes when your existing deal expires.
Regards
Lee_R