The primary difference between a COPY and a CALL statement in Xlate is that a COPY *ALWAYS* copies something to the output. If nothing is specified, the input value is copied. To do it the way you have coded you need to use a CALL statement and use xpmstore in the if.
OR, you could use an Xlate IF inside your iterate like:
IF 0(0)PID.#13(%f1).[0] eq ==PH
COPY 0(0)PID.#13(%f1).[1] -> Telephone Number
Charlie
