Dear Felix
I am happy to exchange your [OLD PRODUCT, ex. Magna flux compressor, model 452B] (invoice #[INVOICE NUMBER]) with [NEW PRODUCT, ex. model 542X]. [STATE HOW DIFFERENCE IN PRICE WILL BE HANDLED, ex. Since the 542X is priced $987.62 less than the 452B, I have credited your account in that amount.]
Since your satisfaction is our goal, do not hesitate to call me at XXX-XX-XX if I can be of any further assistance.
Regards
Lydia