Image of a dot on new phone

Upgraded my cellphone to the Samsung A3,after a day noticed that there is a dot on the phone always appearing on the screen.<br> Worried it will get bigger returned it to Vodacom,they said they must send it to Cape Town first yo confirm the issue and then decide to replace.<br> I disagree as it is a brand new phone and within the seven day period should be replaced.<br> Have two contracts with Vodacom and have been since cell phones were introduced.