Makefile: call multiline variable inside for loop - makefile

Question

Here's my code:
la := a b c d
lb := 1 2 3 4
define test =
First line $$vara
Second line $$varb
endef
export test
#for vara in $(la); do \
for varb in $(lb); do \
echo $$vara $$varb; \
echo "$$test"; \
done \
done
Later this output will go in a file I'm creating using cat.
I'm expecting something like
a 1
First line a
Second line 1
a 2
First line a
Second line 2
...
But instead I'm getting
a 1
$vara $varb
a 2
$vara $varb
What am I doing wrong?
EDIT: SOLUTION
I used as a base #Beta's answer and changed it a bit to allow it to save the result in a file and send it over SSH to another terminal.
define test
[program:$$s-$$c]\nString 1\nString 2\n...\nThe End.
endef
export test
testmake:
#for s in $(serv); do \
for c in $(cust); do \
ssh user#host "mkdir -p /var/log/$$s/$$c"; \
echo "$(call test)" | ssh user#host "cat > /test.txt"; \
done \
done

Answer 1

This worked for me in GNU Make 3.81 (but there are some fussy little differences between versions, so you may have to tweak it):
define test
echo First line $$vara; \
echo Second line $$varb
endef
export test
some_rule:
#for vara in $(la); do \
for varb in $(lb); do \
echo $$vara $$varb; \
$(call test); \
done \
done
Note that this has the loops in a recipe -- which is what I inferred you were doing. If you want the loops to run outside a rule, the solution will look quite different.