In speakerphone mode, iPhone will pick up clean audio from a distance of several feet. Anywhere in the cubicle should work. It would be less restrictive than a headset cable.

Polycom desktop speakerphone would have more range, but it's larger and you'll risk picking up audio from neighboring cubicles.

If you want something more precise, use a small directional microphone, e.g. Rode has one that plugs directly into an iPhone, https://www.apple.com/shop/product/HMG72ZM/A/røde-microphone...