02,January XXXX

[Name of Recipient]
[Name of the Organization]
[Postal Address]
[City, State Zip Code]

Dear[Name of Recipient]

I sincerely apologize for missing your call.I missed your call at that moment because[the reason for not picking the call].I am sorry for that, and I promise it won’t happen again.

Please, accept my apologies.

Yours
[Your Name]