Hello & Welcome,
If you can confirm that the messages are stored in the INTERNAL answering system of your phone, you can "selectively" erase messages (one at a time) by pressing *4 (star-four) to erase the currently playing message.
If you want to erase ALL messages store, use the *5 (star-five) key sequence.
Either one of those should make some space available - so that new messages can be recorded.
As a reference, I have a link to the electronic (PDF) version of the FULL manual for this system, and the key sequences list above are on page 37 of that manual.
BUT, if your messages are actually stored in a "voicemail" system from your provider, then you will need to get the instructions for your provider - on how to erase messages and make space for new ones.
I hope this helps. Please let me know what you find or if you have any more questions.
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