It's extremely unlikely that handsets could cause a problem. They operate at much lower power than the base stations, and they respond at lower frequencies in the bottom part of the C band.
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Let's be clear about what is happening here. There is a potential issue of interference to radar altimeters from C band cellular, which calculations suggest might happen. For technical reasons, the risk is likely to be greatest in the USA.
At the moment, both sides are walking around the issue by restricting operations and/or reducing reliance on equipment. For obvious reasons, these have to be temporary measures.
What seems to be missing at the moment is any move to test whether the interference would actually exist under normal operations, and to what extent.