What should have to do If customer not know about the work that we have done for him?

[ahsanshabbir240]

Do you know how to deal with an angry client or a frustrated customer?

[imagination7413]

That completely depends on why they're upset. 

If YOU did something wrong, then do your best to fix it. (That includes clear communication.)

If THEY are being unreasonable, check your contract with them. Quote the contract. (The Fiverr Terms of Service count.)

If you were unclear in the contract, then it's your responsibility to fix it.