noun
telephone; phone number
Refers to the device or the contact number itself. Common in written contexts like forms, business cards, and contact sections.
名刺にＴＥＬ：03-1234-5678と書いてある。
The business card says TEL: 03-1234-5678.
noun, noun or participle which takes 'suru'
phone call
Used for the act of calling. Can be used with する to mean 'to make a phone call', though 電話する is more common in everyday speech.
後でＴＥＬするね。
I'll give you a call later.