This works really fine:
\+?\d[\d -]{8,12}\d
Matches:
03598245785
9775876662
0 9754845789
0-9778545896
+91 9456211568
91 9857842356
919578965389
987-98723-9898
+91 98780 98802
06421223054
9934-05-4851
WAQU9876567892
ABCD9876541212
98723-98765
Does NOT match:
2343
234-8700
1 234 765