I assume you're asking if the orthography is a completely accurate representation of the phonetic utterances? If so, then no language is 100% "phonetic". Spoken languages inherently adopt phonemes - which represent single perceived "sounds", which are actually represented in speech by several different sounds. The specific sounds will be different allophones of a single phoneme. These will vary for each speaker depending upon language, dialect, and other factors. A language might possibly have an orthography that is 100% accurate to the phonemic inventory, but only for a single dialect. As soon as the dialect changes or another dialect emerges, the orthography will have to change to be 100% accurate.

For example, when I say "butter" with my North American English accent, I typically say the -tt- part with an voiced alveolar tap. It's represented by "ɾ" in IPA. This sounds close to a "d" sound, but faster. However, if you ask me to slow down and repeat "butter", I'll likely respond with a full on [voiceless alveolar plosive], represented by a "t" in IPA. (Look familiar?) Both [ɾ] and [t] are allophones of the /t/ morpheme in NA English. They're specific sounds that are perceived of as a "t".

Now, I am not an expert on Hindi at all, so I cannot make any specific claims myself regarding particular sounds, but if Wikipedia is reliable here, an example of similar allophony is [w] and [v].

* Side note, I'm condensing a bunch of things in here, so it leaves out some complexity, but it should hopefully express the point that no language will have all of its sounds represented perfectly in orthography.

Voice Alveolar Taps - https://en.wikipedia.org/wiki/Voiced_dental_and_alveolar_tap...

Voiceless Alveolar Plosives - https://en.wikipedia.org/wiki/Voiceless_dental_and_alveolar_...

w/v allophony in Hindi - https://en.wikipedia.org/wiki/Hindustani_phonology#Allophony...