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Vodafone customer service on 191 or Live chat can discuss a change as long as it does mean asking for a tariff cost per month drop.
A discount only has to be applied for if it's an upgrade or new contract @stevie12345
Live Chat is 24/7 so an agent would become available asap when you leave the chat window open.
Customer service on 191 is best tried early in the morning and not on a weekend imo.
They'll officially advise you on your account status and discount.
Current Phone > Samsung Note 9 _512Gb > Model: SM-N960 Hybrid-Duos.
Samsung One Ui / Pie.
Samsung Gear s3 Frontier Watch.
If this was a discounted plan the discount will be with the previous tariff. However, If this is the 15% discount you receive with Vodafone Advantage, every time you change your contract in any way, you will need to rejoin the scheme and reapply the discount and that will mean paying a further £10.00 membership charge. There is further information on this below:
For your price plan change you will need to persevere with Customer Services or a Vodafone Store will be able to change your tariff. Alternatively, look at your online account and the My Vodafone Application, when you keep reaching your data limit you can change your plan from there.
If it is only extra data you need take a look at this link this will save you have to change tariff and reapply your Advantage discount Vodafone Extras