Swiping up notification banner for calls no longer silences the incoming call

Hello, jodiealgar.

Let's start off by checking the helpful steps in this article which can help you silence a call: Answer or decline incoming calls on iPhone - Apple Support. It offers the following options to silence or decline an incoming call:

"Silence a call

1. Press the side button or either volume button.
2. You can still answer a silenced call until it goes to voicemail.

Decline a call and send it directly to voicemail

Do one of the following:

1. Press the side button twice quickly.
2. Tap .
3. Swipe up on the call banner.

You can also swipe down on the call banner for more options.

Do any of the following:

1. Tap Remind Me, then choose when you want a reminder to return the call.
2. Tap Message, then choose a default reply or tap Custom.
3. To create your own default replies, go to Settings  > Phone > Respond with Text, then tap any default message and replace it with your own text.

Note: In some countries or regions, declined calls are disconnected without being sent to voicemail."

Let us know if we can help with anything else at all or if this doesn't settle your issue. Thanks and have a fabulous day!