No, 0203 numbers are not free to call from any EE mobile or landline home phone. They’re generally not free on any device, on any network in the UK.
The exception to this rule is when you have spare free minutes in your contract or bundle.
0203 numbers are London based phone numbers, and like all geographic numbers (beginning 01 and 02) and 03 numbers, they are charged at standard rate. All 01, 02 and 03 numbers, including London’s 020 numbers (including the 0203 subdivision) are all charged at standard rate when calling from an EE phone.
Exception: when you have spare inclusive free minutes
The only time when 0203 numbers are free on EE is when you have free minutes included in your contract or bundle. If you have so many free minutes that you won’t use them up even if you call the 0203 number, then the 0203 number you’re calling is effectively free (because it only eats into your spare free minutes). But if you don’t have an excessive free minutes allowance on your EE phone then you will be charged at standard rate else your precious free minutes will be eaten into.
What numbers are free on EE?
The only truly free numbers on EE, are freephone numbers – these include emergency numbers such as 999 and the classic freephone number ranges beginning 0800 and 0808. These are true freephone numbers because they don’t cost anything to call and they don’t eat into any free minutes that you may have on your account.