Hello,
I am afraid I won't tell you anything new here but if you believe that these protocols are unexpected on your serial line and you are sure they are not generated by your own equipment, then by all means, talk to your provider. It might not necessarily be only his MPLS misconfigured, but perhaps other devices somehow leaking into your connection. Certainly your ISP would be interested as well.
Please let us know if there is anything interesting discovered!
Best regards,
Peter