My serial number seems to be incorrectb

Exchange account?

What has this got to do with Serial Number of your device?

Can't send of receive email messages? -->

Check your Outbox and try to send the email again with these steps:

• In Mail, tap Mailboxes in the upper-left corner.
• Tap Outbox. If you don't see an Outbox, then your email was sent.
• Tap an email in the Outbox. Make sure that the recipient's emailaddress is correct.
• Tap Send.

If you can't send email on your iPhone, iPad, or iPod touch ...

Make sure that your Notification settings are correct for the Mail app:

1. Go to Settings, then tap Notifications.
2. Tap Mail, then tap an email account.
3. Adjust your Alerts, Sounds, and Badges.

If you can't receive email on your iPhone, iPad, or iPod touch ...

If you are refering to SMS messages...

SMS, MMS, WiFi Call, Call Forwarding, Call Waiting, Call Merge, Conference Call, Hotspot, Voice Mail all are Carrier Specific features. Contact your Carrier (Cellular Service Provider), the agency who issued the SIM / eSIM to you.

susannah97 wrote:

screen keeps reapeearing saying password incorrect enter the password for the exchange account

It would be better if you can please re-post with a screenshot, in order to understand the phenomenon better. Images / pictures speak louder than words. Do not provide any personal credentials, such as email id, apple id, IMEI number, Serial Number, Phone number, Order ID, if you are sharing a map ensure your location is not identifiable. Etc.