Todd I've had no success with the above suggestions and must ring off now as I have to go out. Sorry we have not been successful.
I'm not sure whether your suggestions solved the problem but I've found that if I move the incoming call icon rapidly to the right then I get connected to the caller.
I'm glad that your issue is resolved.
"Forwarding calls" feature was turned on. So, when you reject incoming call (if you drag the phone icon to the left) all calls will be automatically diverted to your voicemail. I have provided you with the codes and manual instruction how to remove it.
Remember: codes *#21#, *#61# XXXXX *#67# XXXXX forward all your call to the voicemail.
To divert calls instantly without having to ring - *#21#
To divert unanswered calls (rings for 21 seconds) - *#61#
To divert calls whenever your line is engaged - *#67#
To cancel all forwarding - #21#, #61# XXXXX #67#.
After removing the "forward calls" feature, all you need to do is to answer call dragging the phone icon to the right (check the picture below).
Please don't hesitate to ask if you need more information. I will be happy to help with any follow up questions.