Hi Wedgie7,
If you can't hear the person on the other end of your call, the steps in this article may be helpful: If you hear no sound or distorted sound from your iPhone, iPad, or iPod touch speaker
1. Remove all screen protectors, films, or cases from your device.
2. Check the speaker opening to see if it's blocked or dirty. On iPhone only, make sure that the receiver isn't blocked or dirty.
3. If necessary, clean the speaker or receiver opening with a small, soft-bristled brush. Make sure that the brush is clean and dry.
4. Go to Settings > Sounds (or Settings > Sounds & Haptics), and drag the Ringer and Alerts slider back and forth a few times. If you don't hear any sound, or if your speaker button on the Ringer and Alerts slider is dimmed, your speaker might need service.
5. If you hear sound, try making a call with your iPhone and turn on speakerphone. On iPad or iPod touch, make a FaceTime call. If you still can't hear, or hear static or crackling, then your network or reception could be the issue. Try to call again later, or from a different location.
If you need more help, reach out to Apple Support directly so they can look into this with you further. They can be contacted here: Get Support or by calling the most applicable phone number from this list: Contact Apple for support and service.
Regards.