100M : Broadband pricing and tier increase options

[Matty125125]

Hi, I am considering resubscribing to VM broadband and note there is a current promotion through MSE for 100mbps for 24gbp per month (plus 50gbp voucher). I dont need tv, phone or sim as have contracts with other providers. If I take up this offer, assume I can upgrade to the higher tiers? Looking at the price points (outside of the offer) it appears there is a jump of £5 per tier increase so am I right thinking 200mbps should be 29gbp and then 350mbps would be 34gbp? or would I lose the discounted rate if I change tiers? I would phone VM but bearing in mind the current situation and call centre resources thought I would ask if anyone here has experience of this first? Thanks for any help...