Here are some options (among the hundreds of floral shops in SD). These tend to be big florists, so I am sure that they would accept credit cards over the phone.
Flores Dominicanas, S.A. Av. Romulo Betancourt (Antigua Prol. Bolivar) No. 345 B. Sto. Dgo. Tel. (809) 533-9850 Fax. (809) 535-3122
Flores Antillanas Abraham Lincoln 998 Tel. (809) 544-0946/47/48 & 544-1373 Fax. (809) 549-7096
Calizflor Av. 27 de Febrero No. 338, Sto. Dgo. Tel. (809) 562-2155/566-7687 (evening) Fax. 540-6270
Jardin Rosas Rojas, S.A. Salvador Sturla, No. 14, casi esquina Tiradentes (Calle del Club Naco, Sto. Dgo. Tel. (809) 566-2281/565-1728/567-8777 Fax. 542-5332
Hope this helps,
Natasha