There are two options: Either you just want to improve Spoken English or you also want to get a Diploma or Certificate of Spoken English.
For first, the key is simple i.e. speak in English whenever you find any chance to speak with any fellow. Talk to yourself in English whenever you are alone. Use this one site on regular basis and, believe me, you will find the difference. http://effortlessenglishclub.com/

If you want to get a Spoken English Diploma or Certificate too, join NUML. This option is ever better than AIOU's TEFL.

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"But screw your courage to the sticking place,
And we'll not fail." _Shakespeare, 'Macbeth')