Informal use of 'plus'

Enjoy 20% savings on buffet lunch or dinner plus get a complimentary plate of Yee Sang worth RM40 with our Credit Card.

I have seen the above advertising message in a newspaper, and I have brought it up here because I have noticed a non-standard usage of the ‘plus’.

‘Plus’ is normally used as a noun or a preposition or an adjective. In the above case, it is used as a conjunction which is regarded as informal.

The sentence can be improved with just a slight change as “Enjoy 20% savings on buffet lunch or dinner plus a complimentary plate of Yee Sang worth RM40 with our Credit Card” (that is deleting the word ‘get’ and then ‘plus’ will become a preposition) or “Enjoy 20% savings on buffet lunch or dinner and get a complimentary plate of Yee Sang worth RM40 with our Credit Card” (that is replacing ‘plus’ with ‘and’ which is a proper conjunction).