What plan are you currently on? Is it a handset plan? And are you currently within the last 30 days or out of contract?
If you are early upgrading, sometimes there is a restriction on the types of plan you can take as it must maintain a similar cost or higher.
When in the last 30 days or out of contract, these restrictions should not apply and you should have full choice over your plans to upgrade.
Another thing which can affect your choices is your perceived Flex Pay eligibility. On the EE Site for new plans, most of the plans shown are Flex Pay (separate device and airtime, device can be 24 or 36 months) plans but these may not be suitable/available for all customers.
If you're not sure on why your upgrade choices are not satisfactory, you could always call EE on 150 and ask the upgrades team.
Additionally if the system is not letting you take a Flex Pay plan, you could request that a credit referral process be carried out to re-assess your eligibility for these plans. Not entirely sure how they do it, but if you express that you'd like to take Flex Pay then they should be able to advise you on this.
