LDAP otherPager never updates correct field in AD

LDAP otherPager never updates correct field in AD

We have a custom form for users to update their details on our Intranet.
The General Attribute is Extension, which is linked to the custom attribute which calls otherPager as the LDAP name.
When this is updated, it updates the Pager attribute rather than the otherPager attribute.
Any ideas why this would occur?

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