Do you have more context? Looking through the Oxford English Dictionary, there are at least two possible meanings that don't rely on the telephone that were in use during the mid-18th century. The first is would mean to "To rouse (a person) from sleep, esp. at a prearranged time.". Examples:

1711 R. Steele Spectator No. 132. ⁋1 The next Morning at Day-break we were all called.

1832 Tennyson May Queen i, in Poems (new ed.) 90 You must wake and call me early, call me early, mother dear.

Another era appropriate example would be "to call" meaning to "pay a short visit to a person". I'm used to this as a call on someone, but it was apparently also quite common without the preposition. Again, period-appropriate examples:

1728 C. Cibber Vanbrugh's Provok'd Husband iii. 54 You will call me at Lady Revel's?

1853 E. C. Gaskell Cranford xv. 299 One morning, within a week after I arrived, I went to call Miss Matty, with a little bundle of flannel in my arms.

(There are thirty-three separate entries for "call" as a verb, many of them with several sub-entries in the OED, plus an almost equal variety of "call" used in phrasal verbs, so I may have missed a meaning).

I'm not sure that either of those meanings makes sense in the context of the show's dialogue, but both would be period appropriate.