Either
(A) They connected you instead of the MIL
or
(B) They lie.
The router should show you whether it has an ADSL signal via LED or similar. If it hasn't, go back and tell them it doesn't work.
You may think I am just being a pedant with reply A, but I have heard of people booking up the wrong number for ADSL and then, due to poor checks or whatever, finding that they have installed ADSL for somebody else entirely. Classic cock up maybe, but illustrative of how these things can go pear shaped.
Conan