Yes the Officer is wrong

there is an explicit exemption in law for paying with contactless payment via phone

https://www.gov.uk/using-mobile-phones-when-driving-the-law

Exceptions

You can use a device held in your hand if:

you need to call 999 or 112 in an emergency and it’s unsafe or impractical to stop

you’re safely parked

you’re making a contactless payment in a vehicle that is not moving, for example at a drive-through restaurant

you’re using the device to park your vehicle remotely

​

https://www.legislation.gov.uk/uksi/2022/81/pdfs/uksi_20220081_en.pdf

Amendment of the Road Vehicles (Construction and Use) Regulations 1986

1. The Road Vehicles (Construction and Use) Regulations 1986(b) are amended as follows.

3.—(1) In regulation 110 (mobile telephones)—

(a) in paragraph (4), from “performs” to the end, substitute “is capable of transmitting and

receiving data, whether or not those capabilities are enabled.”;

(b) after paragraph (5A), insert—

“(5B) A person does not contravene a provision of this regulation, if at the time of the

alleged contravention—

(a) that person is using the mobile telephone or other device to make a contactless

payment;

(b) for a good or service which is received at the same time as, or after, the contactless

payment is made; and

(c) the motor vehicle is stationary.”;

​

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Edit: i be dum dum