The ISP assigned to a Static Residential Proxy normally cannot be edited in place after purchase.
If the proxy page in Overview or My Proxies shows a replacement option, open it, review the available choices, and confirm the change. Replacement options depend on current inventory and may assign a new IP address.
If the replacement option is not available, or you selected the wrong ISP when ordering, contact Support as soon as possible with your order ID and proxy ID. Support can review the available options, but a specific ISP or replacement cannot be guaranteed.