Your male friend asking you to marry him and you saying 'yes' sounds like the proper phrasing for marriage has not been done, since it consists of the woman proposing to the man, saying 'zawwajtuka nafsi 'ala sidaq al-ma'lum', meaning 'I marry myself to you with an agreed mahr'. The man then says 'qabiltu al-tazwij 'ala sidaq al-ma'lum', meaning 'I accept the marriage with the agreed mahr'. Prior to this, you should have both agreed what mahr [marriage gift] he should give you. According to Wikishia: "The Marriage formula should be recited in correct manner. If even one letter is changed in the formula which changes the meaning, the contract will be void."
If this has been fulfilled, then your marriage would technically be valid, but a word should be said about the issue of 'technically fulfilling the law' while not fulfilling its spirit. Marriages can often be contracted that do not in practice honour the respect of either party. Being technically married Islamically does not guarantee that the situation itself supports that respect. It is wise to be wary of being exploited or manipulated, or coerced into a situation that is not beneficial or appropriate for you in the long term. Being asked over the phone raises doubts about whether you are being given the proper respect, even if it were a long distance proposal.