There are exceptions since the Portuguese brought tea from India to Europe by sea, and still they call it "cha"
https://english.stackexchange.com/questions/18152/british-us...
"Char" as in "cuppa char?" is the usual spelling (would you like a cup of tea?)
According to this: http://www.rmg.co.uk/discover/explore/cup-char it is likely that "char" is derived from Chinese (another country with rather a lot of languages - would the real Chinese please stand up!)
Are just some Indian words loaned by English.
Two interesting words that Punjabi/Hindi has loaned from French is Savon (sabun) and Cartouche (Kartoos).
Also as far as i can tell "cha" is far more common than "char" in the British Isles.
No, it isn't. "Char" is always the spelling I have encountered here (in 47 years).