Wordpress Plugin Adaptation

Adaptation of an existing plugin thats used to send sms messages after woocommerce orders are placed to the person ordering and also an SMS message to the store owner to say there is a new order.
This is an existing plugin, that needs the following things changing:
API changed to a new URL ( paramaters saying the same)
Change to API Key ONLY with no option for username/password
Correction of at least 1 know error, see screen shot. The plugin will not allow the creation of a 'Sent From' entry.
Addition of an addition field, the plugin works using API keys to connect to a specific Custard SMS account, an additional field is required so the store owner can select which sub-group that the data goes to.
The plugin needs rebranding to 'Custard SMS'

Full API documentation is available, just the URL needs changing

Required skills:
Wordpress
API
Woocommerce

Timescales - Within 7 days